Real Materialism 2003

in Russellian monism, ed. T Alter and Y. Nagasawa (Oxford 2015) Real Materialism (with new postscript) Galen Strawson first published in Chomsky and his Critics, ed. L. Antony and N. Hornstein. Oxford: Blackwell. ——————————————————————————————————— ‘Trinculo might have been referring to modern physics in the words, “This is the tune of our catch, played by the picture of Nobody”.’ Eddington (1928: 292) Love like Matter is much Odder than we thought. Auden (1940, ‘Heavy Date’) 1 Introduction1 Materialism is the view that every real, concrete2 phenomenon3 in the universe is physical. It’s a view about the actual universe, and for the purposes of this paper I am going to assume that it is true. It has been characterized in other ways. David Lewis once defined it as ‘metaphysics built to endorse the truth and descriptive completeness of physics more or less as we know it’.4 This can’t be faulted as a terminological decision, but it seems unwise to burden materialism—the view that every real concrete phenomenon in the universe is physical— with a commitment to the descriptive completeness of physics more or less as we know it. There may be physical phenomena which physics (and any non-revolutionary extension of it) cannot describe, and of which it has no inkling, either descriptive or referential.5 Physics is one thing, the physical is another. ‘Physical’ is a natural-kind term—it is the ultimate naturalkind term6—and no sensible person thinks that physics has nailed all the essential properties 1 This paper is an attempt to elaborate on ‘Agnostic materialism’ (Strawson 1994: 43–105), in which I argued that experiential phenomena must be among the fundamental physical phenomena, and that we must be radically ignorant of the nature of the physical in certain ways. Trailers appeared in Strawson 1998 and 1999. Daniel Stoljar and I discovered a strong and encouraging convergence in our views when I gave this paper at the University of Boulder, Colorado in 1998 (see Stoljar 2001). In this reprinting I’ve added a few more quotations and references. 2 By ‘concrete’ I simply mean ‘not abstract’. It’s natural to think that any really existing thing is ipso facto concrete, non-abstract, in which case ‘concrete’ is redundant, but some philosophers like to say that numbers (for example) are real things—objects that really exist, but are abstract. 3 I use ‘phenomenon’ as a completely general word for any sort of existent, a word that carries no implication as to ontological category (the trouble with the general word ‘entity’ is that it is now standardly understood to refer specifically to things or substances). Note that someone who agrees that physical phenomena are all there are, but finds no logical incoherence in the idea that physical things could be put together in such a way as to give rise to non-physical things, can define materialism as the view that every real, concrete phenomenon that there is or could be in the universe is physical. 4 1986: x; when I cite a work I give the date of first publication, or occasionally the date of composition, while the page reference is to the edition listed in the bibliography 5 Physics is trivially referentially complete, according to materialism, in so far as its object of study is the universe, i.e. the whole of concrete reality. There may nevertheless be specific, smaller-scale phenomena of which physicists have no descriptive or referential inkling. 6 Failure to recognize this simple point, long after the existence of natural-kind terms has been generally acknowledged, is one of the more disastrous legacies of positivism. (Compare the survival of the ‘regularity theory of causation’ after the abandonment of phenomenalism.) 1 of the physical. Current physics is profoundly beautiful and useful, but it is in a state of chronic internal tension.7 It may be added, with Russell and others, that although physics appears to tell us a great deal about certain of the general structural or mathematical characteristics of the physical, it fails to give us any further insight into the nature of whatever it is that has these structural or mathematical characteristics—apart from making it plain that it is utterly bizarre relative to our ordinary conception of it. It is unclear exactly what this last remark amounts to (is it being suggested that physics is failing to do something it could do?), but it already amounts to something very important when it comes to what is known as the ‘mind–body problem’. For many take this to be the problem of how mental experiential phenomena can be physical phenomena given what we already know about the nature of the physical. But those who think this are already lost. For we have no good reason to think that we know anything about the physical that gives us any reason to find any problem in the idea that mental phenomena are physical phenomena. If we consider the nature of our knowledge of the physical, we realize with Eddington that ‘no problem of irreconcilability arises’ (1928: 260). Joseph Priestley saw this very clearly over two hundred years ago, and he was not the first. Noam Chomsky reached essentially the same conclusion over thirty years ago, and he was not the last (see e.g. Chomsky 1968: 6–8, 98; 1988: 142–7; 1994 passim; 1995: 1–10; 1996: 38–45; 1998: 437–41; compare Crane and Mellor 1990). Most present-day philosophers take no notice of it and waste a lot of time as a result. Much of the present debate about the ‘mind–body’ problem is beside the point. 2 Terminology I’m going to use the plural-accepting, count-noun form of the word ‘experience’ for talking of experiences as things (events) that may (as we presume) have non-experiential being as well as experiential being. And I’m going to reserve the adjective ‘experiential’ and the plurallacking form of the noun ‘experience’ for talking about the qualitative character that experiences have for those who have them as they have them, where this qualitative character is considered wholly independently of everything else. The phenomenon of experiential8 qualitative character is part of what exists—it is part of reality, whatever its ontological category—and it is important to have some unequivocal way of referring to it and only to it. One could express this terminological proposal by saying that ‘experiential phenomena’ and ‘experience’ (plural-lacking form) refer in a general way to: that part of reality which one is left with when, continuing to live and think and feel as one does, one engages in an old sceptical thought experiment and imagines that the ‘external world’, including one’s own body, does not exist. They refer to the part or aspect of reality one has to do with when one considers experiences specifically and solely in respect of the experiential qualitative character they have for those who have them as they have them, and puts aside the fact that they may also be correctly describable in such non-experiential terms as ‘a 70–20–30 Hertz coding triplet across the neurons of area V4’.9 7 I have in mind the old quarrel between general relativity theory and quantum mechanics, but there is also turmoil in cosmology. 8 ‘Qualitative’ has to be qualified by ‘experiential’ because experiences also have non-experiential qualitative character, according to materialists (every non-relational property of a thing contributes to its qualitative character). Having made the point, I will either bracket ‘experiential’ or follow common practice and omit it. 9 Churchland 1995: 202. Obviously ‘correctly describable’ doesn’t entail ‘fully describable’. Note that one also puts aside the fact that they can be correctly described in such non-experiential terms as ‘a perception 2 3 Realistic materialism Realistic materialists—realistic anybodys—must grant that experiential phenomena are real, concrete phenomena, for nothing in this life is more certain.10 They must therefore hold that they are physical phenomena, although physics contains only predicates for non-experiential being, and so cannot characterize the qualitative character of experiential being in any way. It may at first sound odd to use the word ‘concrete’ to characterize the qualitative character of experiences of colour, gusts of depression, thoughts about diophantine equations, and so on, but it isn’t odd, because ‘concrete’ simply means ‘not abstract’.11 For most purposes one may take ‘concrete’ to be coextensive with ‘possessed of spatiotemporal existence’, although this will be directly question-begging in some contexts.12 It may also sound odd to use ‘physical’ to characterize mental phenomena like experiential phenomena: many materialists talk about the mental and the physical as if they were opposed categories. But this, on their own view, is like talking about cows and animals as if they were opposed categories. Every concrete phenomenon in the universe is physical, according to materialists, so all mental phenomena, including experiential phenomena, are physical phenomena, according to materialists: just as all cows are animals. So what are materialists doing when they talk, as they so often do, as if the mental and the physical were entirely different? What they may mean to do is to distinguish, within the realm of the physical, which is the only realm there is, according to them, between the mental and the non-mental, or between the experiential and the non-experiential; to distinguish, that is, between mental (or experiential) features of the physical, and non-mental (or nonexperiential) features of the physical.13 It’s this difference that is in question when it comes to the ‘mind-body’ problem; materialists who persist in talking in terms of the difference between the mental and the physical perpetuate the terms of the dualism they reject in a way that is inconsistent with their own view. I use the words ‘mental’ and ‘non-mental’ (‘experiential’ and ‘non-experiential’) where many use the words ‘mental’ and ‘physical’ simply because I assume, as a (wholly conventional) materialist, that every real concrete phenomenon is physical, and find myself obliged to put things in this way (compare Chomsky 1968: 98). There’s tremendous resistance to abandoning the old mental/physical terminology in favour of the mental/non-mental, experiential/non-experiential terminology, although the latter seems to be exactly what is required. Many think the old terminology is harmless, and a few are not misled by it: they consistently use ‘physical’ to mean ‘non-mental physical’. But it sets up the wrong frame of thought from the start, and I suspect that those who are never misled by it are members of a small minority. When I say that the mental, and in particular the experiential, is physical, and endorse the view that ‘experience is really just neurons firing’, I mean something completely different of the Eiffel Tower’. 10 Following Lewis 1994 I make no distinction between ‘materialism’ and ‘physicalism’. 11 If ‘immaterial souls’ existed, they would of course be concrete phenomena. 12 Experiential phenomena would be concrete phenomena even if space and time as we currently conceive of them were not really real. 13 One needs to distinguish between mental and experiential phenomena because although all experiential phenomena are mental, not all mental phenomena are experiential, on the ordinary view of things. Certain dispositional states—beliefs, preferences, and so on—are generally acknowledged to be mental phenomena although they have no experiential character (there are also powerful reasons for saying that there are occurrent mental phenomena that are non-experiential). 3 from what some materialists have apparently meant by saying such things. I don’t mean that all aspects of what is going on, in the case of conscious experience, can be described by current physics, or some non-revolutionary extension of it. Such a view amounts to radical ‘eliminativism’ with respect to consciousness,14 and is mad. My claim is different. It is that the experiential (considered just as such)15—the feature of reality we have to do with when we consider experiences specifically and solely in respect of the experiential character they have for those who have them as they have them—that ‘just is’ is physical. No one who disagrees with this is a remotely realistic materialist. When aspiring materialists consider the living brain, in discussion of the ‘mind–body problem’, they often slide into supposing that the word ‘brain’ somehow refers only to the brain-as-revealed-by-current-physics-and neurophysiology. But this is a mistake, for it refers just as it says, to the living brain, i.e. the living brain as a whole, the brain in its total physical existence and activity. Realistic—real—materialists must agree that the total physical existence and activity of the brain of an ordinary, living person, considered over time, is constituted by experiential phenomena (if only in part) in every sense in which it is (assumed to be) constituted (in part) by non-experiential phenomena characterizable by physics. Real (realistic) materialists can’t think that there is something still left to say about experiential phenomena once everything that there is to say about the physical brain has been said. At the same time, they can’t think that physics and neurophysiology can say everything there is to say about the brain, because physics and neurophysiology contain no predicates for experiential phenomena (considered just as such). 4 Materialism further defined Materialism, then, is the view that every real concrete phenomenon is physical in every respect, but more needs to be said, for experiential phenomena—together with the subject of experience, assuming that that is something extra—are the only real, concrete phenomena that we can know with certainty to exist,16 and as it stands this definition of materialism doesn’t even rule out ‘idealism’—the view that mental phenomena are the only real phenomena and have no non-mental being—from qualifying as a form of materialism! There’s a sense in which this consequence of the definition is salutary (see e.g. §§14–15 below), but it may nonetheless seem silly to call an idealist view ‘materialism’. Russell is right to say that ‘the truth about physical objects must be strange’ (1912: 19), but it still seems terminologically reasonable to take materialism to be committed to the existence of non-experiential being in the universe, in addition to experiential being, and I shall do so in what follows. In fact I think the most plausible version of materialism is panpsychist or panexperientialist materialism (see Strawson 1994: 62, and the quotation from Eddington on p. 000 below), in which case we should override this terminological preference. But that is a subject for a different paper. It’s also reasonable to take materialism to involve the claim that every existing concrete phenomenon has non-mental, non-experiential being, whether or not it also has mental or experiential being. Applied to mental phenomena, then, materialism claims that each particular mental phenomenon essentially has non-mental being, in addition to mental being. 14 Some readers doubt this, but it follows from the fact that current physics contains no predicates for experiential phenomena at all, and that no non-revolutionary extension of it could do so. 15 The parenthesis is redundant given the definition of ‘experiential’ in §2. 16 Unless the existence of experiential phenomena of kinds that we know to exist entails the existence of non-experiential phenomena. See n. 18 below. 4 This is, I think, a standard understanding of materialism.17 In this paper, then, I’ll assume, that all realistic materialists take it that there is both mental and experiential being and non-mental, non-experiential being. Must all realistic monists also take it that there is non-mental, non-experiential being? Many would say Yes, on the grounds that it is not remotely realistic to suppose either that there is, or might be, no non-mental or non-experiential being at all. But the question of what it is to be (metaphysically) realistic is far harder here than it is when it is merely the existence of experience that is in question. For the purposes of this paper I will again assume that any realistic position does take it that there is non-mental or non-experiential being in addition to mental and experiential being, for this assumption accords with ordinary conceptions, and my main argument does not require me to challenge it. But it is at best an assumption, which I believe to be false in fact. Idealists, of course, reject the assumption that realistic monism requires acknowledgement of non-mental, non-experiential phenomena, and I will enter a number of reservations along the way.18 It’s clumsy to oscillate between ‘mental’ and ‘experiential’, or constantly double them up, and in the next few sections I’ll run the discussion in terms of the mental/non-mental distinction (such as it is). This said, all my examples of mental phenomena will be experiential phenomena, for they suffice to make the relevant point and are, in the present context, what matter most. It may be added that the reference of the term ‘experiential’ is much clearer than that of the essentially contestable term ‘mental’, and that the latter may in the end deserve the treatment proposed for the term ‘physical’ in §15 below. Nevertheless it seems best to begin in this way.19 I will quote Russell—post-1926 Russell—frequently when discussing materialism, for my views converge with his in certain respects, and he has been wrongly ignored in recent discussion.20 He was still inclined to call himself a ‘neutral monist’ at that time, but he is equally well read as a thoroughgoing materialist.21 He rejects materialism in name, pointing out that ‘matter has become as ghostly as anything in a spiritualist séance’—it has, he says, disappeared ‘as a “thing”’ and has been ‘replaced by emanations from a locality’22—, but he grants that ‘those who would formerly have been materialists can still adopt a philosophy which comes to much the same thing. They can say that the type of causation dealt with in physics is fundamental, and that all events are subject to physical laws’ (1927b: 126–27). And this, in effect, is what he does himself.23 17 In the case of experiences, it amounts to saying that they are not just experiential phenomena, although experiential phenomena are of course part of what constitutes their existence. Note that to distinguish between mental being and non-mental being is not to claim to know how to draw a sharp line between them. The starting situation is simply this: we know there is mental being, and we assume, as conventional materialists, that this is not all there is. 18 In Strawson 1994 (pp. 134-44) I argue that there couldn’t be experiential or experiential content phenomena of the sort with which we are familiar unless there were also non-experiential phenomena; I now think that that argument fails (for reasons given in Strawson 2003), and that all reality could be experiential in nature compatibly with the truth of everything that is true in physics. 19 I discuss the difference between ‘experiential’ and ‘mental’, and the vagueness of ‘mental’, in Strawson 1994 (see e.g. pp. 136–44 and ch. 6). Here I’m trying to avoid the issue as far as possible. 20 See, however, Lockwood 1981. 21 See e.g. Russell 1927b: 110, 119, 123, 126, 170. I don’t understand everything Russell says and may misrepresent him. I aim to take what I think is right from his views without attempting exegesis, and I’ll sometimes detour from the main argument in Russellian directions. 22 1927b: 78, 84. N. R. Hanson (1962) spoke similarly of the ‘dematerialization of matter’, and Priestley (1777) made essentially the same point. See also Lange 1865, quoted in the next note. 23 In his introduction to Lange’s History of Materialism, Russell notes that ‘physics is not materialistic in the old sense, since it no longer assumes matter as permanent substance’ (1925: xix), and he may have the following passage from Lange in mind: ‘We have in our own days so accustomed ourselves to the abstract notion of forces, or rather to a notion hovering in a mystic obscurity between abstraction and concrete 5 5 ‘Mental’ and ‘non-mental’ It may seem odd to take ‘mental’ as the basic positive term when characterizing materialism, but one isn’t a thoroughgoing materialist if one finds it so. For all materialists hold that every concrete phenomenon in the universe is physical, and they are neither sensible nor realistic if they have any inclination to deny the concrete reality of mental phenomena like experiential phenomena.24 It follows that they have, so far, no reason to find it odd or biased to take ‘mental’ rather than ‘non-mental’ as the basic term. — ‘Surely it would be better, even so, to start with some positive term “T” for the nonmental physical, and then define a negative term, “non-T”, to cover the mental physical; or use a pair of independently positive terms?’ There are two good reasons for taking ‘mental’ as the basic positive term, one terminological, the other philosophical. The terminological reason is simply that we do not have a convenient positive term for the non-mental (obviously we can’t use ‘physical’, and there is no other natural candidate). The philosophical reason is very old: it is that we have direct acquaintance with—know—fundamental features of the mental nature of (physical) reality just in having experience in the way we do, in a way that has no parallel in the case of any non-mental features of (physical)25 reality. We do not have to stand back from experiences and take them as objects of knowledge by means of some further mental operation, in order for there to be acquaintance and knowing of this sort: the having is the knowing.26 This point has often been questioned, but it remains immovable. Russell may exaggerate when he says that ‘we know nothing about the intrinsic quality of physical events except when these are mental events that we directly experience’ (1956: 153; my emphasis), or that ‘as regards the world in general, both physical and mental, everything that we know of its intrinsic character is derived from the mental side’,27 for it’s arguable that the spacetime character of the world is part of its intrinsic character, and, further, that we may have some knowledge of this spacetime character. I don’t think he exaggerates much, however. He’s on to something important, and the epistemological asymmetry between claims to knowledge of experiential being and claims to knowledge of non-experiential being is undeniable, however comprehension, that we no longer find any difficulty in making one particle of matter act upon another without immediate contact. We may, indeed, imagine that in the proposition, “No force without matter”, we have uttered something very Materialistic, while all the time we calmly allow particles of matter to act upon each other through void space without any material link. From such ideas the great mathematicians and physicists of the seventeenth century were far removed. They were all in so far still genuine Materialists in the sense of ancient Materialism, that they made immediate contact a condition of influence. The collision of atoms or the attraction by hook shaped particles, a mere modification of collision, were the type of all Mechanism and the whole movement of science tended towards Mechanism’ (1865: 1.308, quoted in Chomsky, 1996: 44). 24 This is so even if ‘eliminativism’ about other candidate mental phenomena—dispositional phenomena like preferences, beliefs, and so on—is worth serious discussion. 25 The word ‘physical’ is bracketed because it is redundant, here as elsewhere. See §14. 26 Compare Shoemaker’s idea (rather differently applied) that many mental states and goings on are ‘constitutively self-intimating’ (1990). See also Maxwell 1978: 392, 396. 27 1927a: 402; my emphasis. See Lockwood 1989: 159: ‘Consciousness ... provides us with a kind of “window” on to our brains, making possible a transparent grasp of a tiny corner of material reality that is in general opaque to us ... . The qualities of which we are immediately aware, in consciousness, precisely are some at least of the intrinsic qualities of the states and processes that go to make up the material world— more specifically, states and processes within our own brains. This was Russell’s suggestion.’ 6 unfashionable. The asymmetry claim that concerns me is not the claim that all epistemic contact with concrete reality involves experience, and that we are inevitably a further step away from the thing with which we are in contact when it is a non-experiential phenomenon. It is, rather, the claim that we are acquainted with reality as it is in itself, in certain respects, in having experience as we do. This second claim revolts against the tendency of much current epistemology and philosophy of mind, but there is no reason why it should trouble thoughtful materialists, and I will offer a brief defence of it in §13. Here it is worth noting that it’s fully compatible with the view that there may also be fundamental things we don’t know about matter considered in its experiential being.28 6 Aside: ‘as it is in itself’ Does one need to defend the phrase ‘as it is in itself’, when one uses it in philosophy? I fear one does, for some think (incoherently) that it is somehow incoherent. Still, it is easy to defend. The supposition that reality is in fact a certain way, whatever we can manage to know or say about it, is obviously true. To be is to be somehow or other. Nothing can exist or be real without being a certain way at any given time.29 And the way something is just is how it is in itself. This point is not threatened by the suggestion that our best models of the behaviour of things like photons credit them with properties that seem incompatible to us—wave-like properties and particle-like properties, for example. What we learn from this is just that this is how photons affect us, given their intrinsic nature—given how they are in themselves, and how we are in ourselves. We acquire no reason to think (incoherently) that photons do not have some intrinsic nature at any given time. Whatever claim anyone makes about the nature of reality—including the claim that it has apparently incompatible properties—just is a claim about the way it is. This applies as much to the Everett ‘many-worlds’ theory of reality as to any other. Some think that what we learn from quantum theory is that there is, objectively, no particular way that an electron or a photon is, at a given time. They confuse an epistemological point about undecidability with a metaphysical claim about the nature of things. The problem is not just that such a claim is unverifiable. The problem is that it’s incoherent. For whatever the electron’s or photon’s weirdness (its weirdness to us: nothing is intrinsically weird), its being thus weird just is the way it is. So we may talk without reservation of reality as it is in itself. Such talk involves no (allegedly dubious) metaphysics of the Kantian kind. Its propriety derives entirely and sufficiently from the thought that if a thing exists, it is a certain way. For the way it is just is how it is in itself. 7 Structure and structured So much, for the moment, for our theoretical conception of the mental: it has some securely anchored, positive descriptive content, and we can know that this is so; for whatever the best general account of the mental, it includes experiential phenomena in its scope; and 28 Not only facts about experience in sense modalities we lack, or (e.g.) about the brightness-saturation-hue complexity of seemingly simple colour-experience, but also, perhaps, murkier facts about its composition, and also, perhaps, about the ‘hidden nature of consciousness’ postulated by McGinn 1991: chs. 3 and 4. 29 If you are worried about the concept—or reality—of time, drop the last four words. 7 experiential phenomena are not only indubitably real; they are also phenomena part of whose intrinsic nature just is their experiential character; and their experiential character is something with which we are directly acquainted, however hard we may find the task of describing it in words. This is so even if we can make mistakes about the nature of our experiences, and even if we can do so even when we consider them merely in respect of their (experiential) qualitative character (see e.g. Dennett 1991a: ch. 11). It is so even if we differ dramatically among ourselves in the qualitative character of our experiences, in ways we cannot know about. Our theoretical conception of the mental, then, has clear and secure descriptive content. (Don’t ask for it to be put further into words; the anchoring is sufficiently described in the last paragraph.) Our theoretical conception of the non-mental, by contrast, remains, so far, a wholly negative concept. It has, as yet, no positive descriptive content. Can anything be done about this? On one reading, Russell thinks not: the science of physics is our fundamental way of attempting to investigate the non-mental being of physical reality, and it cannot help us. ‘Physics is mathematical’, he says, ‘not because we know so much about the physical world, but because we know so little: it is only its mathematical properties that we can discover. For the rest, our knowledge is negative.’ ‘We know nothing about the intrinsic quality of physical events except when these are mental events that we directly experience.’ On this view, neither physics nor ordinary experience of physical objects give us any sort of knowledge of the intrinsic nature of non-mental reality.30 Is Russell right? Something needs to be said about his use of the word ‘intrinsic’. It is potentially misleading, and it helps to consider other ways in which he puts the point. Thus he talks regularly of the ‘abstractness’ of physics. The knowledge it gives is, he says, ‘purely formal’. It reveals the abstract ‘structure’ of physical phenomena while saying nothing about their ‘quality’ (1927a: 392, 382, 388). I am not sure that the distinction between structure and quality is clear, or fundamental in such a way that it holds ‘all the way down’,31 but (putting that doubt aside) it seems that the fundamental distinction that Russell has in mind can be expressed by saying that it is a distinction between how X is structurally disposed and what X is apart from (over and above) its structural disposition.32 Physics gives the structure, but not the structure-transcendent nature, of the thing that has the structure. If we say that truths about how X is structurally disposed have purely structure-specifying content, while truths about what X is over and above its structural disposition also have structure-transcendent content, or, more simply, non-structural content, then we may say that ‘non-structural’ covers everything that Russell 30 Russell 1927b: 125, 1956: 153. Lockwood 1989: ch. 10 contains some illuminating pages on Russell and a useful historical note on versions of the idea that precede Russell’s. See also Maxwell 1978, whose Russellian approach is treated sympathetically in Chalmers 1996: 153–4 (and see index), and Chalmers 1997: 405–6. Jeremy Butterfield and Bas van Fraassen have pointed out to me the link here to John Worrall’s ‘structural realism’; see e.g. Worrall 1989 and Ladyman 1998. Eddington explicitly endorses ‘structuralism’ in 1939 and also makes the point clearly in Eddington 1920 and 1928. 31 Structure is a matter of quality because a thing’s qualitative character, exhaustively considered, is a matter of all aspects of how it is, and its structural character is an aspect of how it is. The converse claim— that quality (in spacetime) is in some sense a matter of structure—sounds a bit mystical, but it can on further reflection begin to seem hard to rebut, even when one maintains, as one must, a sharp distinction between epistemology and metaphysics. ( The distinction between form and content may seem more robust, but may also succumb.) 32 It seems (subject to the doubt expressed in the last footnote) that this distinction must be a real one—that if there is structure, there must be something structured. Only extreme positivistic irresponsibility, or failure to ‘realize what an abstract affair form [or structure] really is’. Russell 1927a: 392, can make this seem questionable. 8 has in mind when he talks of the ‘intrinsic’ nature of things.33 One might dramatize Russell’s idea by saying that physics can be thought of as a formal system which remains, in a peculiar sense, an uninterpreted formal system, even though we know that it applies to something=x—reality, the universe—and even though it is elaborated specifically in causal response to x. On this ‘Ramseyfied’ view, we may suppose that the universe has features that are structurally isomorphic to the structures delineated in the equations of physics, but we have no account of the non-structural nature of the thing that has the structure(s) in question.34 So we are (to pursue the metaphor) in the peculiar position of having a known, concrete application (and so, in one sense, an interpretation) for a formal system, without that application constituting a model (in the sense of model-theoretic semantics) that can confer positive descriptive meaning on its terms. In being the subject matter of physics, the universe provides it with a merely referential model or object, of which it gives a merely structurespecifying description. Physics is about the physical, and may give a correct abstract representation of its structural disposition as far as it goes; but it does not and cannot tell us anything about what the physical actually is, over and above the fact that it exemplifies a certain formal structure.35 8 The non-mental—space Back now to the question whether physics can endow our general theoretical conception of the non-mental with any positive descriptive (not merely referential) content. Russell in 1927 thinks not. I disagree because correct structural description of a thing is already description of a feature of its intrinsic nature. But this disagreement is merely terminological, and the real question is this: Can one go any further than structure-specifying content, when attempting to give a satisfactory theoretical characterization of the non-mental? Again, Russell in 1927 thinks not. It seems to me, however, that we may be able to go a little further. For I think that our ordinary conception of space may get something fundamental right about the nature of reality as it is in itself, and hence about the intrinsic nature of reality—something that survives even after the finite-but-unbounded curved gravity-constituting spacetime of relativity theory (or the ten-or eleven-or twelve-dimensional spacetime of one of the leading versions of string theory) has been granted to be closer to the truth. 33 At one point Russell also takes it that position in spacetime is an intrinsic property of things. Considering the relation between a perception and the object it is a perception of, he remarks that ‘we cannot say whether or not it resembles the object in any intrinsic respect, except that both it and the object are brief events in space-time’ (1927b: 118). 34 When thinking of structural isomorphism, it is helpful to consider a version of an old example: the structural isomorphism between (1) sound waves produced by an orchestra playing Sibelius’s ‘Valse Triste’ that are registered as (2) vibrations of a condenser plate in a microphone and sent as (3) electrical signals to a recording device that stores them as (4) pits on the surface of a compact disk that is then read as (5) digital information by a machine that transmits this information in the form of (6) radio waves to (7) a receiver that puts it through (8) an amplifier to (9) speakers that give rise to (10) sound waves that give rise to (11) electrical impulses in the auditory nerve that give rise to (12) neural occurrences in the auditory cortex and elsewhere that are conscious auditory experiences. There is a structural description that captures the respect in which all these phenomena are the same (assuming no significant loss of information even at the stage of conscious hearing). The abstract character of this description is revealed precisely by the fact that this is what it does: capture the respect in which all these substantially different phenomena are— structurally—the same. Compare Wittgenstein 1922: 4.0141. 35 In 1928, a year after the publication of The Analysis of Matter, Max Newman published a conclusive objection to the pure form of this view, as Russell immediately acknowledged (1967–9: 413–14). See Demopoulos and Friedman 1985. 9 I’m tempted to hold up my hands, like G. E. Moore, and to consider, not my hands, but the space—by which I mean only the spatial extension36—between them, and to say: ‘This is space (spatial extension), and it is real, and I know its nature, in some very fundamental respect, whatever else I do not know about it or anything else (e.g. the fact that it is an aspect of spacetime).’ On this view the ordinary concept of space, or indeed the concept of spacetime, in which (I claim) a fundamental feature of our ordinary conception of space survives, has correct non-structural descriptive content. It does not relate only to ‘what we may call the causal skeleton of the world’, (Russell 1927a: 391), if to say this is to say that it does not capture any aspect of the non-structural nature of the world. It has non-structural content, and can transmit this content to our more general conception of the non-mental.37 Russellians may object as follows ‘This line of thought is profoundly natural, but it depends on a fundamentally false imagining. It involves the conflation of ‘objective’ spatial extension, spatial extension ‘as it is in itself ’ (where this is taken as a merely referential, structural-equivalence-class specifying term with no pretension to non-structural content) with the phenomenological space (or spaces) associated with perception. It involves an almost irresistible but entirely fatal failure to ‘realize what an abstract affair form really is’.38 All those, like yourself, who think that it is viable are ‘guilty, unconsciously and in spite of explicit disavowals, of a confusion in their imaginative picture’ of reality (Russell 1927a: 382; my emphasis). In reply I think that some who take this line may be suffering from excessive empiricism. They take it that the notion of spatial extension—or indeed shape—that we possess is essentially informed by the character of our sensory experiences, and in this I think they are mistaken. It may well be true that sensory experiences of specific kinds are necessary for the acquisition of concepts like SHAPE or SPACE, in the case of beings like ourselves.39 Such concepts can nevertheless float free of the different possible sensory bases of their acquisition and subsequent deployment, without ipso facto becoming ‘merely’ formal or structurespecifying in character. It’s easy to see that grasp of the content of SHAPE (say) does not require essential reference to any specific sensory experience. It suffices to point out that exactly the same concept of shape—that is, the concept of shape, for there is only one—can plausibly be supposed to be fully masterable by two different creatures A and B on the basis of sensory experiences in entirely different sensory modalities familiar to us—sight and touch.40 One has to endorse a rather crude form of meaning-empiricism or conceptempiricism to suppose that A and B do not—cannot—have the same concept, as they do geometry together. A concept is not a faint copy or transform of a sensory experience. It is, precisely, a concept. That’s one point. Another, crucial in this context, is that the concept of shape or space that A and B have in common is not an entirely abstract or purely formal concept, as the supporters of Russell seem to suggest. There is more to A and B sharing the specific concept SHAPE or SPACE than there is to their sharing mastery of the principles of an uninterpreted 36 I am not at all concerned with the ‘substantivalist’ versus ‘relationalist’ debate about the nature of space. Cf. Hirsch 1986: 251–4. I will not here consider the ‘direct realist’ view that we may have some real insight into the non-mental nature of force, say, or causation, as a result of experiencing pushes and pulls and so on in the way we do. 38 Russell 1927a: 392. One could say that it is this point that Newman turns back against Russell (see n. 35). 39 I use small capitals for names of concepts. 40 One may contrast the case of a congenitally blind person with the hypothetical case of a fully sighted person congenitally paralysed and devoid of tactile or any other somatosensory sensation—before thinking of superintelligent echolocating bats and aliens with other sensory modalities. 37 10 formal system that is in fact suitable for the expression of shape configurations or spatial relations although they know it only as an uninterpreted formal system. It is precisely because pure form is such a very ‘abstract affair’, as Russell says, that the concept of shape or space that A and B can have in common in spite of their different sensory experiences cannot be supposed to be a matter of pure form. To think that it is a matter of pure form is to miss out precisely their grasp of the spatiality of space—of that which makes their grasp of the concept of space more than grasp of (say) an abstract metric. The concept has non-structural content. It’s true that this content is abstract in one sense: it is abstract relative to all the particularities of sensation, in a way that is sufficiently indicated by reference to the fact that different creatures can acquire it (the very same concept) on the basis of experience in entirely different sensory modalities. It is indeed, and essentially, a non-sensory concept (see Evans 1980: 269–71; McGinn 1983: 126). But it is not purely abstract in Russell’s sense, because (to repeat) it involves grasp of the spatiality—rather than what one might call the mere abstract dimensionality—of space.41 Spatiality is not abstract dimensionality: the nature of abstract dimensionality can be fully captured by a purely mathematical representation; the nature of spatiality cannot. One can give a purely mathematical representation of the dimensionality of space, but it won’t distinguish space from any other possible threedimensional ‘space’, e.g. the emotional state-space of a species that have just three emotions, love, anger, and despair. Obviously questions arise about the precise nature of the non-structural content of concepts like SHAPE and SPACE, about what it is, exactly, to grasp the spatiality of space, given that SHAPE and SPACE may be fully shared by A, B, superbats, and others. But in the present context I am inclined just to hold up my hands again.42 Russellians may be unimpressed. Michael Lockwood, in particular, is sympathetic to the idea that knowledge of spacetime structure is not knowledge of any feature of the ‘intrinsic’ or non-structural nature of reality. In doing physics, Lockwood says, we may grasp the abstract structure exemplified by space while having ‘no conception of its content: i.e. what it is, concretely, that fleshes out this structure. (For all we know, on this view, Henry More and Newton may be right in equating space with God’s sensorium!)’43 But I am prepared to grant this. I am prepared to grant that we cannot rule out the possibility that space is God’s sensorium,44 or something even more unknown, and that there is therefore a sense in which we may have no idea of what it is that ‘fleshes out’ the abstract structure exemplified by space. For it may still be true that one grasps something fundamental about the non-structural nature of space in thinking of it as having, precisely, spatiality, rather than mere abstract dimensionality. If space is God’s sensorium, so be it: God’s sensorium 41 Even if no finite sensory-intellectual being can possess SHAPE or SPACE without having, or without at least having grasp of the nature of, some form of sensory experience, it does not follow that specification of the content of the concept it possesses necessarily involves reference to any features of sensory experience. 42 If empiricists press me further I will offer (a) the suggestion that sensory modalities that differ qualitatively at first order (i.e. in the way that sight and touch do) may be said to be crucially similar at second order in as much as they are ‘intrinsically spatial’ in character, (b) the speculation that this similarity can itself be understood as a kind of similarity of (experiential) qualitative character, (c) the acknowledgement that it may be that one must be capable of experience in some ‘intrinsically spatial’ sensory modality or other (even if only in imagination) in order to possess SHAPE or SPACE, (d) the reservation that even if a non-conceptual experiential modality must be in play, it is not obvious that this must be a sensory modality. This, however, is too simple (I discuss the question further in Strawson 2002). 43 Personal communication. Eddington agrees: ‘We know nothing about the intrinsic nature of space’ (1928: 51–2). 44 After setting aside the problem of evil. 11 may really have the property of spatiality. Between a fat-free, purely mathematical and thus wholly abstract representation of the structure of space and a partly structure-transcending conception of space as God’s sensorium (or some such) lies a third option: an ostensibly less rich but still structure-transcending conception of space as specifically spatial (hands held up) in its dimensionality. Some may think this a fine point, but it is (I take it) a huge step away from Russell’s claim that we know nothing about the intrinsic quality of non-mental events.45 I am not claiming that we do know something about the non-structural nature of space, only that we may (I hold up my hands, I move them apart—but my sense of the vulnerability of this claim has increased since I wrote this paper in 1997). This claim allows, as it should, that there may well be more to space than we can know. SPACE, like PHYSICAL, is a natural-kind concept, and there are some atrociously good reasons for thinking that there is more to space than we know or can fully understand. In addition to the (already weighty) points that physical space is non-Euclidean, and is itself something that is literally expanding,46 and the non-locality results,47 and questions about the nature of the vacuum, and widespread agreement that ‘there is no good a priori reason why space should be a continuum’, 48 I for one still can’t fully understand how space and time can be interdependent in the way that they demonstrably are. We are also told on very good authority that gravity is really just a matter of the ‘curvature’ of space, and that string theory is an immensely promising theory of matter (especially after the ‘second superstring revolution’ and the growth of M-theory, and especially when it comes to understanding gravity) that entails that there are at least ten spatial dimensions.... These points reopen the connection to the mind–body problem. For as they pile up, one can’t reputably hold on to the old, powerful-seeming Cartesian intuition that there is a ‘deep repugnance’ or incompatibility between the nature of conscious experience and the nature of spatial extension—the intuition that ‘the mental and the spatial are mutually exclusive categories’ (McGinn 1995: 221). We have direct acquaintance with fundamental features of conscious experience—experiential features—just in having it; but we really have no good reason to think that we know enough about the nature of space—or rather, about the nature of matter-in-space-considered-in-so-far-as-it-has-non-mental-being—to be able to assert that there is any repugnance.49 And if conscious experience is in time, as almost everyone agrees, then it is in spacetime, given the way in which space and time are demonstrably interdependent—in which case it is in space in every sense in which it is in time. 45 ‘We know nothing about the intrinsic quality of physical events except when these are mental events that we directly experience’ (1956: 153). Perhaps Russell takes this distancing step himself in his 1928 reply to Newman (see n. 35): ‘It was quite clear to me, as I read your article, that I had not really intended to say what in fact I did say, that nothing is known about the physical world [the non-mental world as opposed to the mental world, in my terminology] except its structure. I had always assumed that there might be copunctuality between percepts and non-percepts, and even that one could pass by a finite number of steps from one event to another compresent with it, from one end of the universe to the other ... spaciotemporal continuity of percepts and non-percepts was so axiomatic in my thought that I failed to notice that my statements appeared to deny it’ (1967–9: 413). 46 In such a way that the correct answer to the question ‘Where was the Big Bang taking place at the first moment in which it made sense to say that it was taking place anywhere?’ is ‘Right here’, wherever you are. 47 Bell 1987; for an informal illustration see Lockwood 1996: 163–4. 48 Isham and Butterfield 2000. 49 Foster 1982: ch. 5 and McGinn 1995 give forceful presentations of the repugnance intuition. At one point McGinn makes the funky suggestion that consciousness might be a manifestation of the non-spatial nature of pre-Big Bang reality (223–4). I think he moves in a better direction when he shifts to the very different claim that ‘consciousness tests the adequacy of our spatial understanding. It marks the place of deep lack of knowledge about space’ (230). 12 Note that it follows that even if our notion of space can confer some non-structural content on our best theoretical conception of the non-mental, it cannot confer any content that is guaranteed to distinguish it from any fully articulated theoretical conception of the mental, although we still intuitively feel it to fit with the former conception in a way in which we don’t feel it to fit with the latter.50 9 The non-mental—spin, mass, and charge I have proposed that our theoretical conception of the non-mental may be able to acquire some non-structural content from its first lieutenant, the concept of space. Can it acquire any more? Well, I think that our more particular spatial concepts of shape, size, position, distance, and local motion (I raise my hands and bring them together) may also get something right about reality as it is in itself, and so contribute to the non-structural content of our general theoretical conception of the non-mental; I think Locke may be essentially right in his view that some of our ideas of primary qualities correctly represent how things are in themselves, although his account needs recasting.51 It may also be that our ordinary conception of time gets something right about the nature of reality (both experiential and non-experiential)—even if we need to conceive time as part of spacetime in order to think about it properly. I just don’t know.52 Going on from space, time, extension, shape, position, distance, and motion, in the attempt to give a positive characterization of the non-mental, one may want to mention properties like spin, mass, charge, gravitational attraction, ‘colour’ and ‘flavour’ (in the quantum-theoretic sense). But one will have to bear in mind that our grasp of these things—any grasp of them over and above that which is conveyed by their intimate relation to concepts of space and time—is expressed merely in equations;53 and the truth in Russell’s remark that physics is mathematical not because we know so much about the physical world, but because we know so little. So although I like to think that concepts of space and time carry non-structural content, I do not think this can be true of any of these other concepts considered independently of their relations to concepts of space and time. Here Russell is right: we know nothing of the non-mental non-structural nature of—for example—electrical phenomena apart from their spacetime structure; all we have are equations.54 But even if knowledge of spacetime structure is all we have, in the way of non-structural knowledge of the nature of the non-mental, it makes a huge difference to the case. Consider the difference between a characterization of the forces of electrical attraction and repulsion in 50 I’m grateful to Mark Sainsbury for encouraging me to make this point more explicit. Locke’s talk of ‘resemblance’ between primary qualities and ideas of primary qualities is unfortunate in as much as it suggests a (mere) picturing relation, and Russell, 1927a: 385, holds that Locke is definitely wrong. 52 Perhaps it gets something right in an Augustinian sense, according to which we can be said to know what time is even though we find we don’t know what to say when someone asks us what it is. 53 Unless some ‘direct realist’ account of our understanding of force is defensible. See n. 37. Note, though, that no sensible direct realist view can suppose that we derive understanding of the nature of force directly from the merely sensory character of experiences of pushes, pulls, and so on; that would be like thinking that we can get some real insight into the nature of electricity from the qualitative character that experiences of electric shocks have for us (compare Evans 1980: 270). Somehow, the sensory experiences would have to be the basis of an abstract, essentially cognitive, general, non-sensory concept of force. 54 The word ‘non-mental’ is not redundant in the last sentence, for it seems very plausible to suppose that consciousness is an electrical phenomenon, whatever else it is; in which case it may be said that we do have some knowledge of the non-structural nature of electrical phenomena just in having conscious experience. 51 13 which their spatial character (the way they decrease with increasing distance) is given a purely mathematical, abstract-dimensional interpretation, and one in which it is given a genuinely spatial interpretation. Consider any account of anything in which time relations have a merely mathematical abstract representation, and one in which the temporality of time is somehow represented. 10 Hens’ eggs I want now to give a further characterization of what it is to be a genuine materialist. But I must first answer an objection that occurs to many. —‘It seems to follow, from your claim that we have no knowledge of the non-structural, intrinsic or as we may say N-intrinsic nature of things, that we cannot know that there are tables and chairs and hens and hens’ eggs and ‘that hens’ eggs are generally laid by hens’ (Moore 1905–6: 64). But this is a chair I’m sitting in, and it’s made of wood, and this is a hen, and this is a hen’s egg, and this hen laid it. These are all facts I know, and they are N-intrinsic facts—ultimate, absolute truths—about the nature of reality. They must be included in any true and full account of the history of the universe.’ My reply to this objection is similar to Moore’s a hundred years ago. I agree that we know many such truths, but I take it, as a materialist, that hens are wholly made of the fundamental constituents of matter that physics discusses, and that when we consider our knowledge of these fundamental constituents we encounter the crucial and entirely general sense in which we know nothing about the fundamental N-intrinsic nature of matter. As far as I can see, this ignorance is entirely compatible with the sense in which we do have knowledge of the Nintrinsic of reality in knowing that there are hens, and what hens are, and what wood is, and so on. And this compatibility is no more surprising than the fact that I can know that this is a statue without knowing what it is made of. —‘But we know what hens are made of—carbon, hydrogen, and oxygen, mostly—and we know what carbon, hydrogen, and oxygen are made of—electrons and quarks with various characteristics. Physics gives us knowledge of the properties of these things. If you think that it fails to give us any knowledge of their ultimate, N-intrinsic nature that’s because you think that a thing is more than its properties. But that’s just bad old metaphysics. A thing is not in any sense more than its properties.’ I agree that there is an irredeemably difficult but inescapable sense in which it is true to say that a thing is not more than its properties—I agree that ‘in their relation to the object, the properties are not in fact subordinated to it, but are the way of existing of the object itself’ (Kant 1781: A414/B441, substituting ‘object’ and ‘property’ for ‘substance’ and ‘accident’ respectively)— but the present claim is not that a concrete phenomenon must be more than its properties, but that it must be more than its purely formal or structural properties. If you say that this is more bad metaphysics, a yearning for lumpen stuff, our disagreement will be plain. My reply will be that you have evidently forgotten ‘what an abstract affair form really is’. A concrete phenomenon must be more than its purely formal or structural properties, because these, considered just as such, have a purely abstract mathematical representation, and are, concretely, nothing—nothing at all. It is true that we get out of the realm of the purely abstract when we add in spatiotemporal properties, on my account, but a thing’s non14 structural properties can’t consist only in its spatiotemporal properties—at least so long as spacetime is conceived merely as a dimensional manifold with no physical or substantial nature.55 Here, then, we return to the point that—the sense in which—we have no knowledge of the N-intrinsic nature of things in spite of the sense in which it is true to say that we know what hens and hens’ eggs are. 11 True materialism I have suggested that our general theoretical conception of the mental has substantial nonstructural descriptive content, because we have acquaintance with fundamental features of the mental nature of reality just in having experience in the way we do. Our general theoretical conception of the non-mental has substantial structure-specifying content, and I have suggested, with some hesitation, that it may also have crucial and correct non-structural content deriving from spatiotemporal concepts. Apart from this, though, it is arguable (subject to note 45) that we know nothing about the intrinsic or non-structural nature of non-mental reality. With this in place, we may ask what is to be a genuine materialist. The first thing to do is to intone once more that realistic or real materialism entails full acknowledgement of the reality of experiential phenomena: they are as real as rocks, hence wholly physical, strictly on a par with anything that is correctly characterized by physics.56 They are part of physical reality, whatever is or is not the case. It follows that current physics, considered as a general account of the general nature of the physical, is like Othello without Desdemona: it contains only predicates for non-experiential being, so it cannot characterize experiential being at all (recall the definition in §2). It cannot characterize a crucial feature of reality at all. No one who doubts this is a true materialist. Partly for this reason, I think that genuine, reflective endorsement of materialism is a considerable achievement for anyone who has had a standard modern Western education. Materialism must at first provoke a feeling of deep bewilderment in anyone contemplating the question ‘What is the nature of the physical?’ The occurrence of such a feeling is diagnostic of real engagement with the materialist hypothesis, real engagement with the thought that experiential phenomena are physical phenomena just like spatial-extension phenomena and electrical phenomena in so far as they are correctly characterized by physics (or indeed common sense). I think Russell is profoundly right when he says that most are ‘guilty, unconsciously and in spite of explicit disavowals, of a confusion in their imaginative picture of matter’. I suspect that some will be unable to shake off the confusion, although Locke made the crucial move long ago. Some may say that modern science has changed the situation radically since Locke’s time. It has—but only in so far as it has massively reinforced Locke’s point. Perhaps I am generalizing illegitimately from my own experience, revealing my own inadequacy rather than the inadequacy of recent discussion of the ‘mind–body’ problem, but I don’t think so. Genuine materialism requires concerted meditative effort. Russell recommends ‘long reflection’ (1927b: 112). If one hasn’t felt a kind of vertigo of astonishment, when facing the thought, obligatory for all materialists, that consciousness is a wholly physical phenomenon in every respect, including every experiential respect—a sense of having been precipitated into a completely new confrontation with the utter strangeness of the physical 55 56 15 For the importance of this qualification, see n. 89 below. ‘As characterized by physics’ is a necessary qualification; see the remarks about ‘brain’ on p. 000 above. (the real) relative to all existing common-sense and scientific conceptions of it—, then one hasn’t begun to be a thoughtful materialist. One hasn’t got to the starting line.57 Some may find that this feeling recurs each time they concentrate on the mind-body problem. Others may increasingly think themselves—quietistically, apophatically, pragmatically, intuitively—into the unknownness of the (non-mental) physical in such a way that they no longer experience the fact that mental and non-mental phenomena are equally physical as involving any clash. At this point ‘methodological naturalism’—the methodological attitude to scientific enquiry into the phenomena of mind recommended by Chomsky—will become truly natural for them, as well as correct.58 I think it is creeping over me. But recidivism is to be expected: the powerfully open state of mind required by true materialism is hard to achieve as a natural attitude to the world. It involves a profound reseating of one’s intuitive theoretical understanding of nature.59 I say ‘intuitive theoretical understanding of nature’, but it isn’t as if there is any other kind. For (briefly) what we think of as real understanding of a natural phenomenon is always at bottom just a certain kind of feeling, and it is always and necessarily relative to other things one just takes for granted, finds intuitive, feels comfortable with. This is as true in science as it is in common life. I feel I fully understand why this tower casts this shadow in this sunlight, given what I take for granted about the world (I simply do not ask why light should do that, of all things, when it hits stone). I may also feel I understand—see—why this billiard ball does this when struck in this way by that billiard ball. But in this case there is already a more accessible sense in which I don’t really understand what is going on, and it is an old point that if I were to ask for and receive an explanation, in terms of impact and energy transfer, this would inevitably invite further questions about the nature of impact and energy transfer, starting a series of questions and answers that would have to end with a reply that was not an explanation but rather had the form ‘Well, that’s just the way things are’ (see e.g. van Fraassen 1980: ch. 5; Strawson 1994: 84–93). The true materialist outlook may become natural for some, then, but many will find they can maintain it only for relatively short periods of time. It is not a small thing. To achieve it is to have evacuated one’s natural and gripping common-sense ± science-based conception of the nature of the physical of every element that makes it seem puzzling that experiential phenomena are physical. I think it is to be at ease with the idea that consciousness is a form of matter.60 It can help to perform special acts of concentration—focusing one’s thought on one’s brain and trying to hold fully in mind the idea that one’s experience as one does so is part of the physical being of the brain (part of the physical being of the brain that one may be said to be acquainted with as it is in itself, at least in part, because its being as it is for one as one has it just is what it is in itself, at least in part). It is worth trying to sustain this—it is part of doing 57 The only alternative, I think, is that one has a very rare and beautiful intellect. See Chomsky 1994; 1995: 1–10. Chomsky is a clear example of someone who is, methodologically, a true materialist in my sense. I am not sure that he would accept the title, however; he avoids the term ‘materialist’ because of the point made by Lange in n. 23 above, which I try to counter on pp. 000–00 below. 59 In fact one doesn’t have to be a materialist to hold that no defensible conception of the physical contains any element that gives one positive reason to doubt that experiential phenomena are physical. One can hold this even if committed to dualism. 60 I think that it requires realization that this claim is inadequately expressed by saying ‘consciousness is a property of matter’, or even ‘consciousness is a physical property of matter’, given the almost irresistible incentives to metaphysical misunderstanding that are I believe already built into the word ‘property’ (see Strawson 2008b). 58 16 philosophy—, forcing one’s thought back to the confrontation when it slips. At first one may simply encounter the curious phenomenological character of the act of concentration, but it is useful to go on—to engage, for example, in silent, understanding-engaging subvocalizations of such thoughts as ‘I am now thinking about my brain, and am thinking that this experience I am now having of this very thinking—and this subvocalization—is part of the physical activity and being of my brain.’ It is also useful to look at others, including young children, as they experience the world, and to think of the common-or-garden matter that is in their heads (hydrogen, oxygen, carbon, iron, potassium, sodium, and so on). It is useful to listen to music, and focus on the thought that one’s auditory experience is a form of matter.61 12 Knowledge of ignorance Finding it deeply puzzling how something could be physical is not the same as finding something that one takes to be physical deeply puzzling. It is often said that quantum theory is deeply counterintuitive—in its description of the wave-like and particle-like behaviour of fundamental particles, for example—but no one seems to find it puzzling to suppose that it deals wholly with physical phenomena.62 The main reason for this seems to be as follows: WAVE and PARTICLE engage smoothly with standard physics concepts of shape, size, position, motion, and so on. There is, so far, a clear sense in which the two concepts are theoretically homogeneous, or at least nonheterogeneous; they operate on the same, single conceptual playing field of physics.63 But when we try to integrate conscious-experience terms with the terms of physics (and commonsense physics), we find that they entirely lack any such felt theoretical homogeneity, or nonheterogeneity. To this extent, they force constantly renewed bewilderment—in a way quite different from the way in which quantum-mechanical phenomena do—on materialists who like to think they have some sort of coherent, theoretically unified understanding of the overall nature of the physical, however general that understanding may be, and however incomplete in its details. But this is the central mistake: to think that one has some sort of theoretically unified understanding of the overall nature of the physical. Once one realizes that this cannot be true, if materialism is true, things change.64 It begins to look as if there is actually less difficulty in the suggestion that physical phenomena have both experiential and non-experiential being than in the suggestion that photons (for example) behave both like particles and waves. For in the case of experiential terms and non-experiential terms there is no direct clash of concepts of the sort that occurs in the case of the wave-particle duality. Being a wave is incompatible with being a particle, but there is nothing in the possession of non-experiential being that we 61 Perhaps intuitive materialism is not always an achievement, and comes easily, and without positive error, in certain Eastern schools of thought. The requirement that there be no positive error of conception is, however, important. 62 Some may object that there is a compelling description of quantum-mechanical phenomena that completely eliminates the air of mystery attaching to wave-particle duality (see e.g. Deutsch 1997: ch. 2); but it does so at the cost of another large strangeness, because it requires one to accept Everett’s manyworlds hypothesis; and although it may be that this is what one should do, I will continue to use the case of wave-particle duality as an example for the purposes of discussion. (I will also put aside the view that the real intuitive difficulty resides in the phenomenon of superposition rather than in the wave-particle duality.) 63 I try to give more content to the idea of theoretical homogeneity in Strawson 1994: 88–93. Note that one can have a sense that a group of terms is theoretically homogeneous, or at least not problematically heterogeneous, without feeling that one understands the phenomena these terms are used to describe. 64 Although there are plenty of deep puzzles in physics even when mind is put to one side. 17 know to be intrinsically inimical to the possession of experiential being: we simply do not know enough about the nature of non-experiential being to have any good reason to suppose that this might be so. Thus the experiential terms and the non-experiential terms do not in fact actively clash, as the wave and particle terms do. Rather, they fail to connect or engage. One is making progress as a materialist when one has lost all sense of an active clash. It has no scientific or philosophical justification. As Russell says, ‘the physical [sc non-mental] world is only known as regards certain abstract features of its space-time structure—features which, because of their abstractness, do not suffice to show whether the physical world is, or is not, different in intrinsic character from the world of mind’ (1948: 240; see also 247). Arnauld made the essential point in 1641, in his comments on Descartes’s Meditations, and he was not the first.65 Locke in 1689 ‘did not apprehend that there was any real inconsistency between the known properties of body, and those that have generally been referred to mind’.66 Algarotti observes in 1737 that we are as yet but Children in this vast Universe, and are very far from having a compleat Idea of Matter; we are utterly unable to pronounce what Properties are agreeable to it, and what are not, (1737: 2.194) and Hume in 1739 shows a very clear understanding of the point (1739–40: 246–8). Priestley in 1777 argues, with unanswerable force, and by appeal to a scientific conception of the physical that (in essence) still holds good today, ‘that we have no reason to suppose that there are in man two substances so distinct from each other as have been represented’.67 Kant concurs in 1781, although his special terms of debate preclude him from agreeing directly with Priestley’s further materialist claim that ‘mind ... is not a substance distinct from the body, but the result of corporeal organization’; that ‘in man [thought] is a property of the nervous system, or rather of the brain’; that ‘sensation and thought do necessarily result from the organization of the brain’.68 The quality of the mind-body debate is in many ways lower today than at any other time in the last three hundred years. Substance dualism may have looked like a plausible response to the mind-body problem in Descartes’s time, for classical mechanistic materialism, according to which the physical world consists entirely of small, solid, intrinsically inert particles in motion, was then the dominant 65 In Descartes 1641: 2.141–3. Lange (1865) discusses many precursors. Priestley 1777–82: 115. Locke doesn’t fully carry through his point that our ignorance of the nature of the physical means that we lack any good reason to doubt that consciousness is wholly physical; for at one point he says that ‘matter ... is evidently in its own nature void of sense and thought’ (1689: 4.3.6; see also 2.10.5). But he also says that we ‘possibly shall never be able to know whether any material being thinks, or no’, and holds that an omnipotent being could give ‘some systems of matter, fitly disposed, a power to perceive and think’ (4.3.6). The force of the second quotation is less than one might suppose: it does not conclusively establish that Locke thought that God could make matter have such a power intrinsically or in and of itself—i.e. without any special wizardry. But Locke’s correspondence with Stillingfleet very strongly suggests that his considered view is that our ignorance of the nature of the matter is in the end too great for us to have any good reason to claim that matter could not have the power of thought in and of itself (1696–9: 459–62). 67 1777–82: 219. Priestley observes, correctly, that there is no evidence for absolute solidity: ‘I ... define ... matter ... to be a substance possessed of the property of extension, and of powers of attraction and repulsion. And since it has never yet been asserted, that the powers of sensation and thought are incompatible with these (solidity, or impenetrability only, having been thought to be repugnant to them), I therefore maintain that we have no reason to suppose that there are in man two substances so distinct from each other as have been represented.’ 68 Kant 1781: A358–60; Priestley 1777–82: 220, 244, 303. John Toland in 1704 ‘obviously regards thought as a phenomenon which is an inherent accompaniment of the material movements in the nervous system’ (Lange 1865: 1.329). 66 18 view, and Leibniz’s famous image of the mill seemed hard to counter.69 But the strict mechanist understanding of the physical world was fatally undermined by 1687, when Newton published his Principia.70 Since then we have had no good scientific reason to think that mind is not physical. And even before Newton, in the high days of ‘contact mechanics’, there were no philosophically respectable grounds for claiming that mind is not physical. The mechanists or ‘Cartesians’, as Hume calls them, made a wholly unjustifiable move: they ‘established it as a principle that we are perfectly acquainted with the essence of matter’ (Hume 1739–40: 159; my emphasis). That is, they not only assumed that their fundamental theory of matter was sound as far as it went; they also assumed that it went all the way—that it was complete. It is the second of these two false assumptions that causes most trouble, for even if the Cartesians had been right that all physical change is a matter of the motion, contact, and impact of solid particles, they still would not have been justified in claiming that this fact was definitely—knowably—incompatible with some of it also being a matter of conscious goings on. Many today make exactly the same sort of mistake. 13 The reality of appearance I’ve claimed that thoughtful materialism requires draining one’s conception of the nonexperiential physical of any element that, in a puzzling world, makes it seem especially puzzling that the experiential is physical. Many philosophers—all those legions who tried, for most of the twentieth century, to reduce the mental to the non-mental in some way—think this is the wrong way round. They think we have to drain our conception of the experiential of any element that produces special puzzlement, leaving our existing conception of the nonexperiential physical in place. But no substantial draining can be done on the experiential side. In having experience in the way we do, we are directly acquainted with certain features of the ultimate nature of reality, as Russell and others have remarked—whether or not we can put what we know into words in any theoretically tractable way. And this is so whatever it is best to say about any non-experiential (e.g. dispositional) aspects of the mental that there may be. We may certainly hope to develop our understanding of the nature of the experiential; but we can do this only by adding to what we already know of it by direct acquaintance: —‘But in having experience we only have access to an appearance of how things are and are not cognizant, in the mere having of the experience, of how anything is in itself.’71 The reply is immediate. Here, how things appear or seem is how they really are: the reality that is at present in question just is the appearing or seeming. In the case of any experiential episode E there may be something X of which it is true to say that in undergoing E we only 69 ‘We must admit that perception, and whatever depends on it, cannot be explained on mechanical principles, i.e. by shapes and movements. If we pretend that that there is a machine [e.g. a brain] whose structure makes it think, sense and have perception, then we can conceive it enlarged, ... so that we can go inside it as into a mill. Suppose that we do: then if we inspect the interior we shall find there nothing but parts which push one another, and never anything which could explain a perception. Thus, perception must be sought in simple substances, not in what is composite or in machines’ (Leibniz 1720: 150 [Monadology §17]). 70 Locke saw this pretty clearly after reading Newton (see e.g. Locke 1689: 2.23.24, 4.3.29; 1696–9: 467– 8). Chomsky (1995: 4) quotes tellingly from Leibniz and Huygens, who condemned Newton for abandoning sound ‘mechanical principles’ and reverting to mystical ‘sympathies and antipathies’ and ‘inexplicable qualities’. 71 See Dennett 1991a: 365–6, and the reply in Strawson 1994: 51–2. 19 have access to an appearance of X, and not to how X is in itself. But serious materialists must hold that E itself, the event of being-appeared-to, with all the qualitative character that it has, is itself part of physical reality. They cannot say that it too is just an appearance, and not part of how things are, on pain of infinite regress. They must grant that it is itself a reality, and a reality with which we must, in plausibility, be allowed to have some sort of direct acquaintance. As Russell says, we must ‘treat “seeming” with respect’ (1927b: 101). At this point some may try to adapt Ryle-type arguments for the ‘systematic elusiveness of the “I” to the present case (Ryle 1949: 186–9). They may argue that anything that can count as knowledge of experience involves an operation of taking experience as an object that necessarily precludes apprehending it in such a way that one can be said to have access to how it is in itself, rather than merely to an appearance of it. I suspect that this ancient form of argument is invalid even in its original application, where it is used to argue that the putative mental subject of experience can never directly apprehend itself.72 But even if this is not so it has no valid application to the present case—to things like pain and colour-experience. The way a colour-experience is experientially, for the subject of experience that has it, is part of its essential nature—its ultimate reality—as a physical phenomenon. When we claim (with Russell) that to have an experience is eo ipso to be acquainted with certain of the intrinsic features of reality, we do not have to suppose that this acquaintance involves standing back from the experience reflectively and examining it by means of a further, distinct experience. It doesn’t. This picture is too cognitivist (or perhaps too German-Idealist). The having is the knowing. 14 The radiance of reality I’ve argued that the first thing that one needs to do, when it comes to the mind–body problem, is to reflect on one’s ignorance: one’s ignorance of the non-experiential. One’s intuitive theoretical attitude to the nature of the non-experiential needs to evolve until any sense that there is an active clash between experiential terms and non-experiential terms has disappeared, leaving only the awareness that they fail to connect in a way that brings a sense of intuitive understanding. This awareness ought not to be merely a matter of book learning. At this point at least two paths open up for materialists. The first goes deeper into reflection on the nature of understanding in physics. Proceeding down this path, one encounters one’s sense that at least some of the terms of physics (both common-sense and scientific) connect up with one another in a way that justifies a feeling of intuitive understanding of at least some of what goes on in the world. One is then asked to examine (possibly at length) the question of what exactly one supposes this to amount to. Does it really amount to anything very solid? Is it more than a certain kind of feeling one is disposed to get (either innately or as a result of training) when considering some but not other co-occurrences of features in the world? What exactly is its significance (see, again, van Fraassen 1980: ch. 5)? Well, one probably has to go down this path at some point, as a materialist, returning to the questions raised on p. 000. But I will choose another, which has a sunnier aspect. Here one confronts the deep puzzlement one still feels when one considers experiential properties and non-experiential properties and fails to see how they coexist, and, also, one’s persisting feeling that this puzzlement has, in a puzzling world, a very special if not unique status. The question is whether one can do anything about this. I think the answer is Yes. I think 72 20 I argue for this in Strawson 2010. physics can help us—it has already helped us a great deal—by diluting or undermining features of our natural conception of the physical that make non-experiential phenomena appear toto coelo different from experiential phenomena. The basic point is simple, and can be elaborated as follows. At first, perhaps, one takes it that matter is simply solid stuff, uniform, non-particulate: Scandinavian cheese. Then, perhaps, one learns that it is composed of distinct atoms—particles that cohere more or less closely together to make up objects, but that have empty space (to put it simplistically but intelligibly) between them. Then, perhaps, one learns that these atoms are themselves made up of tiny, separate particles, and full of empty space themselves.73 One learns that a physical object like the earth or a person is almost all empty space. One learns that matter is not at all what one thought. Now one may accept this while holding on to the idea that matter is at root solid and dense. For this picture retains the idea that there are particles of matter: minuscule grainy bits of ultimate stuff that are in themselves perfectly solid (in Locke’s phrase), ‘continuum-dense’. And one may say that only these, strictly speaking, are matter: matter as such. But it is more than two hundred years since Priestley (citing Boscovich) observed that there is no positive observational or theoretical reason to suppose that the fundamental constituents of matter have any perfectly solid central part (see also Foster 1982: 67–72, Harré and Madden 1975: ch. 9). In spite of this, a fairly robust conception of truly solid particles survived all the way into pre-1925 quantum mechanics. It suffered its most dramatic blow only in modern (1925 on) quantum mechanics, in which neither the nucleus nor the electrons of an atom are straight-up solid objects, and are much more naturally thought of as fields. It may be said that the basic idea of the grainy particle survives even here, at least in as much as the nucleus and its components are still fairly well localized within a small central region inside the atom (albeit with small ‘tails’ that go out to infinity), and in as much as the probability of finding one of the (far less localized) electrons is significant only within a volume that is normally considered to be the dimensions of the atom. But this commitment to the localization of particles does not in itself amount to any sort of commitment to continuum-dense solidity, but only to fields and repulsive forces that grow stronger without any clear limit when one travels in certain directions (i.e. towards the centre of the field associated with a particle). And whatever is left of the picture of ultimate grainy bits is further etiolated in quantum field theory, in which the notion of the field more fully overrides the picture of grainy particles.74 In this theory it becomes very hard to treat ‘bound’ systems like atoms at all. As for what I’ve been calling ‘empty space’—the supposed vacuum—, it is understood to be simply the lowest energy state of fields like the electron, proton, and photon fields. It turns out to be something which ‘has structure and can get squeezed, and can do work’.75 It may be said that quantum field theory is complicated and ill-understood, but there is a clear sense in which grainy, inert bits of matter, naively conceived, are already lost to us 73 As in the old quantum-theory model of the atom, c.1910–24. The standard way to convey the amount of empty space inside an atom is to say that if the nucleus is imagined to be as big as a 1 mm pinhead, then the nearest electrons—themselves much smaller than the nucleus—are 100 metres away. 74 ‘In the modern theory of elementary particles known as the Standard Model, a theory that has been well verified experimentally, the fundamental components of nature are a few dozen kinds of field’ (Weinberg 1997: 20). We continue to talk in terms of particles because the quantization of the field, whereby each different (normal) mode of vibration of the field is associated with a discrete ladder of energy levels, automatically gives rise to particle-like phenomena so far as observation is concerned. 75 Harvey Brown, personal communication; see Saunders and Brown 1991. Perhaps Descartes was right, deep down, in his theory of the plenum. 21 independently of quantum field theory, given only the fact that matter is a form of energy, and interconvertible with it. This fact of interconvertibility is widely known, however little it is understood, and it seems to me that it further, and utterly, confounds any understanding of matter that takes it to be in any obvious way incompatible with consciousness. To put it dramatically: physics thinks of matter considered in its non-experiential being as a thing of spacetime-located forces, energy, fields, and it can also seem rather natural to conceive of consciousness (i.e. matter apprehended in its experiential being) as a spacetime-located form or manifestation of energy, as a kind of force, and even, perhaps, as a kind of field.76 We may still think the two things are deeply heterogeneous, but we have no good reason to believe this.77 We just don’t know enough about the nature of matter considered in its nonexperiential being; and doubtless there are things we don’t know about matter considered in its experiential being. Those who think speculations like this are enjoyable but not really serious haven’t really begun on the task of being a materialist; they haven’t understood the strangeness of the physical and the extent of our ignorance. It is a long time since Russell argued that ‘from the standpoint of philosophy the distinction between physical and mental is superficial and unreal’, and it seems that physics can back philosophy on this question (Russell 1927a: 402). In fact—and it had to come back to this—we really don’t know enough to say that there is any non-mental being. All the appearances of a non-mental world may just be the way that physical phenomena—in themselves entirely mental phenomena—appear to us; the appearance being another mental phenomenon.78 Whatever you think of this last proposal, lumpish, inert matter, dense or corpuscled, stuff that seems essentially alien to the phenomenon of conscious-ness, has given way to fields of energy, essentially active diaphanous process-stuff that—intuitively—seems far less unlike the process of consciousness. When Nagel speaks of the ‘squishy brain’, when McGinn speaks of ‘brain “gook”’ and asks how ‘technicolour phenomenology ... can ... arise from soggy grey matter’, when the neurophysiologist Susan Greenfield describes the brain as a ‘sludgy mass’, they vividly and usefully express part of the ‘imaginative ... confusion’ in the ordinary idea of matter.79 But physics comes to our aid: there is a clear sense in which the best description of the nature of the non-experiential in non-technical, common-sense terms comes from physics. For what, expressed in common-sense terms, does physics find in the volume of spacetime occupied by a brain? Not a sludgy mass, but an astonishingly (to us) insubstantialseeming play of energy, an ethereally radiant vibrancy. It finds, in other words, a physical object; which, thus far examined, is like any other. Examined further, this particular physical object turns out to have a vast further set of 76 Compare Maxwell 1978: 399; James 1890: 1.147 n. It is arguable that Schopenhauer holds something close to this view. 77 Using this very wording, Kant, 1781–7: B427–8, remarks that the ‘heterogeneity’ of mind and body is merely assumed and not known. 78 Richard Price is consistently outclassed by Priestley in their Free Discussion of the Doctrine of Materialism, but he gets this point exactly right: ‘if ... it comes out that [Priestley’s] account of matter does not answer to the common ideas of matter, [and] is not solid extension, but something not solid that exists in space, it agrees so far with spirit’, or mind (Priestley and Price 1778: 54; Price held that spirit was not only located in space but might also be extended). This is a rather good description of how things have come out, in physics. The account of matter given by current physics does not ‘answer to the common ideas of matter’; it does not take matter to be ‘solid extension’, but rather ‘something not solid that exists in space’. So far, then, it agrees with our understanding of mind or consciousness, although the agreement can only be negative, given that we have no non-mathematical grasp of the non-structural nature of the nonexperiential being of matter—apart (perhaps) from our grasp of its spacetime structure. 79 Nagel 1998: 338; McGinn 1991: 1, 100; Greenfield BBC 21 June 1997. In spite of these quotations I think that all three of these writers are fundamentally on the right track when it comes to the mind-body problem. 22 remarkable properties: all the sweeping sheets and scudding clouds and trains of intraneuronal and interneuronal electrochemical activity which physics (in conjunction with neurophysiology) apprehends as a further level of extraordinarily complex intensities of movement and (non-experiential) organization existing in an n-dimensional realm that we call spacetime although its nature is bewilderingly different from anything we ordinarily have in mind in thinking in terms of space and time. All this being so, do we have any good reason to think that we know anything about the non-mental physical (assuming it exists) that licenses surprise—even the very mildest surprise—at the thought that the experiential is physical? I do not think so. Brains are special, but they are not strange. The ghost in the machine is special, but it is certainly in the machine, and the machine, like the rest of the physical world, is already a bit of a ghost—as ghostly, in Russell’s view, ‘as anything in a spiritualist séance’ (1927b: 78). So when David Lewis says that ‘the most formidable opposition to any form of mind-body identity comes from the friends of qualia’ (1999: 5), i.e. experiential phenomena, there is no reason to agree. The main opposition to (realistic) mind–body identity comes, paradoxically, from its most passionate proponents, who are so strongly inclined to think they know more about the nature of the non-mental physical than they do. Lewis exemplifies the great mistake in his well-known summary account of his position in the philosophy of mind: ‘Remember’, he says, ‘that the physical nature of ordinary matter under mild conditions is very well understood’, (Lewis 1994: 412). But there is no reason to believe this, and every reason to disbelieve it. ‘What knowledge have we of the nature of atoms that renders it at all incongruous that they should constitute a thinking [experiencing] object?’, asks Eddington, who took the existence of experiential phenomena (‘qualia’) for granted: ‘science has nothing to say as to the intrinsic nature of the atom.’ The atom, so far as we know anything about it, is, like everything else in physics, a schedule of pointer readings [on instrument dials]. The schedule is, we agree, attached to some unknown background. Why not then attach it to some-thing of a spiritual nature of which a prominent characteristic is thought? It seems rather silly to prefer to attach it to something of a so-called ‘concrete’ nature inconsistent with thought, and then to wonder where the thought comes from. We have dismissed all preconception as to the background of our pointer readings, and for the most part can discover nothing as to its nature. But in one case— namely, for the pointer readings of my own brain—I have an insight which is not limited to the evidence of the pointer readings. That insight shows that they are attached to a background of consciousness (Eddington 1928: 259–60; my emphasis on ‘silly’) The point is still negative. It may destroy one common source of puzzlement, but it doesn’t offer any sort of positive account of the relation between the play of energy non-experientially conceived and the play of energy experientially apprehended, and some may find it no help at all. Others may say that it is a positive mistake to think that it is especially helpful, on the grounds that there is in the end no more difficulty in the thought that the existence of matter naively and grossly conceived involves the existence of consciousness than there is in the thought that matter quantum-mechanically conceived does so.80 80 They will find Russell’s line of thought equally unnecessary as a way of reaching a conclusion they already fully accept: ‘having realised the abstractness of what physics has to say, we no longer have any difficulty in fitting the visual sensation into the causal series. It used to be thought “mysterious” that purely physical [i.e. non-mental] phenomena should end in something mental. That was because people thought they knew a lot about physical phenomena, and were sure they differed in quality from mental phenomena. We now realise that we know nothing of the intrinsic quality of physical phenomena except when they happen to be sensations, and that therefore there is no reason to be surprised that some are sensations, or to 23 We can grant them their objection for their own consumption (they are likely to be fairly sophisticated philosophers). Many others—not excluding philosophers—are likely to find the negative point rather useful, and I will conclude this section by relating it to three currently popular issues. (1) Eliminativism. Consider any philosopher who has ever been tempted, even momentarily, by the ‘eliminativist’ suggestion that one has to question the reality of the experiential in some way in order to be a thoroughgoing materialist. It is an extraordinary suggestion,81 and what is most striking about it in the present context is that it constitutes the most perfect demonstration in the history of philosophy of the grip of the very thing that it seeks to reject: dualist thinking. The eliminativists make the same initial mistake as Descartes—the mistake of assuming that they understand more about the nature of the physical than they do—but their subjugation to dualist thinking is far deeper than Descartes.82 They are so certain that the physical excludes the experiential that they are prepared to deny the reality of the experiential in some (admittedly unclear) way—to make the most ridiculous claim ever made in philosophy—in order to retain the physical. (The mistake of thinking one may have grasped the essential nature of the physical is perhaps forgivable in the early seventeenth century, but not now.) (2) The hard part of the mind-body problem. It can be seriously misleading to talk of ‘the hard part of the mind-body problem’ (Strawson 1989: 80, 1994: 93; compare McGinn 1989: 1), or ‘the hard problem’ (Chalmers 1995: 200). For this suggests that the problem is clearly posed. It is not, as Chomsky has observed. One might say that it is not sufficiently well defined for us to be able to say that it is hard; for although we have a clear and substantial positive fix on the non-structural nature of experiential reality, we have no substantial positive fix on the non-structural nature of non-experiential reality, apart, perhaps, from its spatiotemporal characteristics. To this extent we have no good reason to think that the mindbody problem is a harder problem than the problem posed for our understanding by the peculiarities of quantum physics. The problem is the nature of the physical, and in particular, perhaps, of the non-mental physical. (3) Zombies. It is, finally, a mistake to think that we can know that ‘zombies’ could exist— where zombies are understood to be creatures that have no experiential properties although they are perfect physical duplicates (PPDs) of experiencing human beings.83 The argument that PPD-zombies could exist proceeds from two premisses: [1] it is conceivable that PPDzombies exist, [2] if something is conceivable, then it is possible. The argument is plainly valid, and (unlike many) I have no great problem with [2]. The problem is that we can’t know [1] to be true, and have no reason to think it is. To be a genuine materialist is precisely to hold that [1] is false, and while materialism cannot be known to be true, it cannot be refuted a suppose that the others are totally unlike sensations’ (1927b: 117). It seems considerably more implausible than Xenocrates’ suggestion that the soul is a self-moving number (see Aristotle De Anima 408b–409a). 82 In fact it is not clear that Descartes does make this mistake, although it is clear that some eliminativists do. Descartes was for a long time seen as a dangerous source of materialist views, and there are some reasons for thinking that his official dualism was motivated partly by the desire to stave off persecution by religious authorities. 83 I don’t know where these zombies come from—but they may be Australian. In the 1980s and early 1990s philosophical zombies were far more plausible creatures: they were standardly defined as outwardly and behaviourally indistinguishable from human beings while having unknown—and possibly nonbiological—insides (see e.g. Dennett 1991: chs. 4, 10, 11), and were, accordingly, of considerable interest to functionalists and behaviourists. (Note added in 2014: it turns out that ‘PPD zombies’ surfaced in Kirk 1974, and featured also in effect in K. Campbell 1970.) 81 24 priori, as it could be if [1] could be known to be true. PHYSICAL is a natural-kind concept, and since we know that there is much that we do not know about the nature of the physical, we cannot claim to know that an experienceless PPD—a perfect physical duplicate, no less— of a currently experiencing human being is even conceivable, and could possibly exist. One needs to be very careful how one embeds natural-kind terms in ‘it is conceivable that’ contexts.84 It is worth adding that anyone who holds that it is as a matter of physical fact impossible for a PPD of an actual, living normally experiencing human being to have no experience must hold that PPD-zombies are metaphysically (if not logically) impossible. Physical impossibility entails metaphysical impossibility in this case, because the question is precisely what is possible given the actual nature of the physical. 15 Realistic monism In §1 I pointed out that the word ‘physical’, as used by genuine materialists, entails ‘real and concrete’: given that one is restricting one’s attention to concrete phenomena, as we are doing here, to say something is a physical phenomenon is simply to say that it is a real phenomenon. But then why bother to use ‘physical’? (compare Crane and Mellor 1990). It has become an entirely empty or vacuous term, in so far as it is supposed to mean anything more than ‘real’. So why not simply use ‘real’? And why bother with ‘real’, given that we’re talking about whatever (concretely) exists, whatever it is? It is redundant. All one strictly needs, to mark the distinctions centrally at issue in the unfortunately named ‘mind–body problem’, are ‘mental’ and ‘non-mental’, ‘experiential’ and ‘non-experiential’.85 One can simply declare oneself to be a experiential-and-non-experiential monist: one who registers the indubitable reality of experiential phenomena and continues to take it that there are also non-experiential phenomena. I nominated this position for the title ‘realistic monism’, having explicitly assumed (p. 000) that any realistic position must take it that there is non-experiential being. This assumption can be backed by an argument that seems at first quite strong—(1) experience (experiential content) certainly exists, (2) experience (experiential content) is impossible without a subject of experience, (3) a subject of experience cannot itself be an entirely experiential (experiential-content) phenomenon, so (4) the existence of experience (experiential content) entails the existence of non-experiential phenomena. But one can have no deep confidence in the correctness of the assumption if one accepts the general principles of ignorance defended in this paper, and this argument for it invites the reply that even if a subject of experience must have some sort of non-experiential being relative to its own experience, its nonexperiential being may be the experience of some other, lower-order, subject or group of subjects, and so on down. I’m not sure this reply is cogent, in fact;86 but nor am I sure that premiss (3) is solid. I propose in any case to leave the assumption that there is nonexperiential being firmly marked as an assumption. —‘You say we can do without the word “physical”. But if one can do without “physical”, then ‘materialist’, used so diligently in this paper, is just as superfluous—vacuous. You’ve 84 It is worth noting that a perfect physical duplicate of an actual human being would have to be governed by the same physical laws. 85 According to the view presented in Strawson 1994: 162–75, the latter pair suffice on their own. 86 I argue that it is in Strawson 2003. 25 already stated that you make no distinction between materialism and physicalism (note 10), and the word ‘materialist’ is deeply compromised by its history. History is two-faced, and I think that ‘materialist’—an adjective formed from the natural-kind term ‘matter’—can be harmlessly and even illuminatingly retained.87 What, after all, is matter? As a materialist, I take it that it is whatever we are actually talking about when we talk about concrete reality. I fix the reference of the term ‘matter’ in this way—giving a chair a kick, perhaps—independently of any reference to theories. I can be certain that there is such a thing as matter, as a realistic materialist monist—one who takes it that experience is wholly material in nature—because I can be certain that there is such a thing as concrete reality: experience, at the very least. What a materialist may still wish to add to this, in spite of Eddington’s powerful doubt, is the insistence that nothing can count as matter unless it has some sort of non-experiential being (see §4); together with the working presumption that current physics is genuinely reality-representing in certain ways, even if any correctness of representation is only a matter of the holding of certain relations of structural correspondence between the nature of matter and the equations of physics. In so far as I am a realistic materialist monist, then, I presume that physics’s best account of the structure of reality is genuinely reality-representing in substantive ways, and that the term ‘materialist’ is in good order. I sail close to the wind in my use of the word ‘matter’, facing the charge of vacuousness and the charge (it is seen as a charge) that it may be hard to distinguish my position from idealism, because that is precisely what one has to do at this point. Kicking another chair, I grant that the term ‘materialist’ has travelled far from some of its past uses, but there is no good reason to think that its meaning is especially tied to its past uses rather than to the current understanding of matter.88And there is a sense in which its past use makes it particularly well worth retaining: it makes the claim that the present position is materialist vivid by prompting resistance that turns out to be groundless when the position is properly understood.89 That is all I have to say about the word ‘materialist’. Some will probably think that I would do better to call myself a ‘neutral monist’, or just a ‘monist’.90 But what about ‘monist’? 87 Here I may differ from Chomsky—but only, I think, on a point of terminology. (Obviously ‘physical’ can also be retained in so far as it is synonymous with ‘material’.) 88 There is, in particular, no good reason to think that it is especially tied to the seventeenth-century conception of matter as something passive and inert. The conception of matter as essentially energyinvolving, or at least as something to which motion is intrinsic, seems to be already present in the work of Democritus and Epicurus. 89 Let me add that I take it that spacetime itself is material (it is a disputed question). In quantum field theory, reality consists of spacetime and a collection of fields defined on spacetime; what we think of as material objects are emergent (in the non-spooky sense) features of these fields. But spacetime is not a merely passive container, for according to general relativity the action-reaction principle applies as between spacetime and matter (this is the phenomenon Pullman, 1998: 351, usefully calls ‘the vacuummatter complementarity, or ... the virtual-material duality of particles’). Moreover, the gravitational field, unlike the other fields, is not distinct from spacetime itself. Rather, the gravitational field, within a given region, just is the spacetime geometry of that region. The structural relations it involves are physical or material because they are spatiotemporal (they are not merely abstract-dimensional). Note also that energy can be stored and propagated within the gravitational field, and hence within the spacetime fabric itself, which again suggests that spacetime is substantial and hence—given materialism—material, in a way that Newtonian space and time, say, are not. (My thanks to Michael Lockwood and Harvey Brown for discussion of this matter.) 90 Neutral monism is not an option on the present view, because we know that experience like ours is part of reality, whatever else is or is not the case, and we know its nature—its ‘ultimate’ nature, if you like—in having it; whatever else is or is not the case. It cannot be supposed to be merely an appearance of something that is in itself quite unlike experience. 26 There is serious unclarity in this notion. Monists hold that there is, in spite of all the variety in the world, a fundamental sense in which there is only one basic kind of stuff or being. But questions about how many kinds of stuff or being there are are answerable only relative to a particular point of view or interest; and what point of view is so privileged that it allows one to say that it is an absolute metaphysical fact that there is only one kind stuff or being in reality? Materialists call themselves monists because they think that all things are of one kind—the physical kind. But most of them also hold that there is more than one kind of fundamental particle, and this claim, taken literally, entails that there isn’t after all any one basic kind of being out of which everything is constituted. For it is the claim that these particles are themselves, in their diversity, the ultimate constituents of reality; in which case there is kind-plurality or stuff-plurality right at the bottom of things. —‘But these particles are nevertheless all physical, and in that sense of one kind.’ To say that they can be classed together as single-substanced in this way is question-begging until it’s backed by a positive theoretical account of why it is correct to say that they are all ultimately (constituted) of one kind (of substance). To claim that their causal interaction sufficiently proves their same-substancehood is to beg the question in another way, on the terms of the classical debate, for classical substance-dualists simply deny that causal interaction entails same-substancehood. The claim that they are all spatiotemporally located also begs the question. For how does this prove same substancehood? It may be replied that all the particles are just different forms of the same stuff—energy. And it may be added that the so-called fundamental particles—quarks and leptons—are not strictly speaking fundamental, and are in fact all constituted of just one kind of thing: superstrings. And these monist approaches deserve investigation—to be conducted with a properly respectful attitude to panpsychism.91 But one can overleap them by simply rejecting the terms of the classical debate: one can take causal interaction to be a sufficient condition of same-substancehood. I think that this is the right dialectical move in the present context, if one wants to retain any version of the terminology of substance. Dualists who postulate two distinct substances while holding that they interact causally not only face the old and seemingly insuperable problem of how to give an honest account of this interaction. They also face the (even more difficult) problem of justifying the claim that there are two substances. As far as I can see, the only justification that has ever been attempted has consisted in nothing more than an appeal to the intuition that the mental or the experiential is utterly different in nature from matter. But this intuition lacks any remotely respectable theoretical support, if the argument of this paper is even roughly right. The truth, as Priestley saw, is that dualism has nothing in its favour—to think that it has does is simply to reveal that one thinks one knows more about the nature of things than one does—and it has Occam’s razor (that blunt sharp instrument) against it. This is not to rule out the theoretical possibility that substance dualism—or pluralism—is in fact the best view to take about our universe for reasons of which we know nothing.92 The fact remains that the objection to dualism just given remains decisive when dualism is considered 91 See e.g. Seager 1995, Strawson 2006a. It shouldn’t be necessary to say that panpsychism certainly doesn’t require one to believe that tables and chairs are subjects of experience. 92 There may be phenomena in the universe that can’t interact causally given their nature (rather than their position in spacetime), or that do so only on the first Thursday of every seventh century, in a highly peculiar way. 27 specifically as a theoretical response to the ‘mind-body problem’. —‘But why persist with “monist”? You might as well call yourself a “neutral pluralist”, for all the difference it makes, and “monist” carries bad baggage. Why not simply call yourself a “non-committal naturalist”, or a “?-ist’?”93 This section stirs up large questions, but I’m not too troubled. In some moods, retaining the assumption that there is non-experiential being, I’m prepared to drop the term ‘monist’ and call myself an ‘experiential-and-non-experiential ?-ist’. At the moment, though, the physics idea (the ancient idea) that everything is made of the same ultimate stuff—that the deep diversity of the universe is a matter of different states or arrangements of the same fundamental ens or entia—that ‘in the whole universe there is only one substance differently modified’ (La Mettrie, 1747: 39)—seems to me as compelling as it is remarkable, and I choose to register my attraction to it with the word ‘monism’.94 Postscript In Mental Reality (1994) I went almost all the way to panpsychist or panexperientialist materialism.95 I argued that real materialists must hold at least some experiential properties to be fundamental physical properties, like electric charge … [they must] hold that experiential properties are—that experientiality is—among the fundamental properties that must be adverted to in a completed or optimal physics (pp. 60, 61–2), i.e. [1] experientiality is among the fundamental properties of physical reality. I noted (p. 77) that [1] didn't entail the fully panpsychist position [2] experientiality is a fundamental property of all physical phenomena, but took [2] to be the most plausible situation given [1].96 I also noted that while it is certain that there is experiential reality, it is simply an assumption on the part of materialist monists “that there is more to physical reality than experiential reality” (p. 74). Most take 93 Sebastian Gardner proposed that I am a ‘?-ist’ in 1990. It’s hard to find satisfactory names, and Grover Maxwell, who holds essentially the same position as I do, calls himself a ‘nonmaterialist physicalist’ (1978: 365), by which he means a physicalist who is a genuine realist about experience. 94 I’m especially grateful to Noam Chomsky, Michael Lockwood and Undo Uus for the leads they have given me. I would also like to thank Lucy Allais, Torin Alter, Harvey Brown, Jeremy Butterfield, Arthur Collins, Tim Crane, Mark Greenberg, Isaac Levi, Barry Loewer, Brian McLaughlin, Philip Pettit, Mark Sainsbury, Simon Saunders, Stephen Schiffer, Peter Unger, Bas van Fraassen, and audiences at the University of Birmingham, CUNY Graduate Center, and Columbia University in 1997 and 1998. 95 I use ‘panpsychism’ and panexperientialism’ interchangeably. ‘Materialism’ does little more than indicate that this panpsychist position remains a thesis about the reality which is the subject matter of physics—the concrete physical or material reality about which we take physics to say many true things (compare p. 000 above). 96 In those days reaching potentially panpsychist conclusions induced a certain bashfulness in analytic philosophers like myself. For greater forthrightness see e.g. Sprigge (1983), Griffin (1998). 28 [3] physical reality has non-experiential being to be essentially definitive of any materialist view, built into the meaning of the words ‘physical’ and ‘material’, but this can’t be taken for granted when physics and metaphysics get serious—recall the quotation from Russell on p. 000.97 In ‘Real Materialism’ I put panpsychist materialism mostly on one side while preparing a more fully panpsychist step forward.98 It is, certainly, a large step from [2], which one might call weak panpsychism, to the strong or pure panpsychist claim that [4] experientiality (experience and subjects of experience) is all there is to concrete physical reality, and one immediately salient alternative to [4] (here I assume for purposes of argument that physical reality involves the existence of a multitude of very small fundamental entities) is micropsychism, according to which (to vary [1] slightly) [5] experientiality is a fundamental property of at least some of the fundamental physical entities but not necessarily all. Plainly micropsychism can be true while panpsychism is false, as noted in Mental Reality (p. 77). One entirely speculative possibility is that only particles whose existence involves the existence of electric charge (this includes neutrons but not e.g. neutrinos, photons or gluons) possess experientiality as a fundamental property. There are many possibilities. With Eddington, Whitehead, and others, I think that [4], pure panpsychism/panexperientialism, is on balance the most plausible form of materialism, the most scientifically 'hard-nosed', theoretically elegant, theoretically parsimonious form of materialism, the form that appears most intuitively plausible when one has thought the matter through. The version I favour performs a ‘global replace’ on physics as traditionally conceived. It proposes that the fundamental intrinsic nature of the reality treated of in physics (energy—see p. 000 above) is wholly a matter of experientiality. In so doing it leaves everything that is correct in physics untouched. It doesn’t have the implausible consequence that stones and tables are subjects of experience. Nor does it put in question the view that the particular qualitative character of the experience of biological subjects of experience such as ourselves is a product of evolution by natural selection. I’m not sure there is any quick way to work one’s way into a proper appreciation of the power of this position after a standard education in analytic philosophy. It’s likely to be ‘hard work … a kind of laziness pulls [one] insensibly back into one’s everyday habits of thought’ (Descartes 1641: 2.15), and ‘we love our habits more than our income, often more than our life’ (Russell 1923: 113). It took me a long time. One is making progress when one sees that ‘panpsychism must be considered a species of naturalism’ (Sellars 1927: 218). One is making further progress when one catches up with Eddington and Co.—noting as one goes that Russell and James, for all their talk of ‘neutral monism’, are 97 It is not in fact well supported by the dictionary definitions of ‘material’ and ‘physical’ in the Oxford English Dictionary (one has to go to definition 21 of ‘matter’ for clear support). 98 In a paper given to a one-day conference in London in 2002 with Frank Jackson and David Papineau (Strawson 2006a). 29 also open to panpsychism (if indeed the supposed neutrality of their fundamental stuff doesn’t collapse into a form of panpsychism). Even if one can’t go all the way one should I believe endorse the thesis of the theoretical primacy of panpsychism. According to this thesis, unprejudiced consideration of what we know about concrete reality obliges us to favour some version of panpsychism, or at the very least micropsychism, over all other positive substantive theories of the intrinsic non-structural nature of reality. In its strongest form, the thesis is not just that it would take extraordinarily hard work to justify preferring any substantive metaphysical position that isn’t panpsychist or micropsychist—however great the difficulties panpsychism and micropsychism may also face.99 It’s rather that it can’t be done. It can’t be done because it requires that one assume the existence of things whose existence one has no reason to assume. It’s intensely natural for us to feel certain that there is non-experiential concrete reality, in addition to the experiential reality we know to exist, so that pure panpsychism must be false. But, first, [6] there is no evidence—there is precisely zero evidence—for the existence of non-experiential reality. Nor can there ever be any. Physics is silent on the question of the intrinsic non-structural nature of concrete reality. 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