mind, brain and identity

Mind, Brain and Identity

Stewart Candlish

Mind, New Series, Vol. 79, No. 316. (Oct., 1970), pp. 502-518.

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111.-MIND, BRAIN AND IDENTITY

THE many discussions of an Identity Theory of mind and brain that have appeared in recent, years have all failed to deal in detail with a question that is of the first importance to anyone seriously considering the adoption of such a theory. This question is whether the identity-conditions of brain processes and what are (too) loosely termed mental events are sufficiently similar to permit their identification. For unless we are going to be rigidly essentialist about identity and suppose not only that all identity-questions are governed both by the Principle of Identity of Indiscernibles and the Principle of Indiscernibility of Identicalsl (of which the latter would prohibit the identities proclaimed in the theoretical reductions of science2) but also that the content of these formal principles is unvarying from case to case, it must be agreed that the concept of identity will figure in the concepts of certain kinds of things in a way that is somewhat different from the way in which i t will figure in the concepts of other kinds of things. When thinking about identity in the past we have been excessively dominated by that kind of identity appropriate to material objects.

Let me clarify these somewhat cryptic remarks by means of an example. By the phrase ' identity-conditions ' I mean to indicate the conditions under which a thing of a certain kind is distinguished as an individual from other things of that kind,

1 These two principles are generally conflated and often conf~~sed. The Principle of Identity of Indiscernibles is this:

' (x)(y){[(P)(Pxr Py)] ~ ( x y)} ' is logically necessary =

The Principle of Indiscernibility of Identicals is this: ' (x)(y){(x= y) 3 [(P)(Px Py)]} ' is logically necessary.

Identity Theorists seem to be inclining to the view that the theory would be scientific rather than metaphysical. See e.y. D. M. Armstrong, A Materialist Theory of the Mind, ch. 6, sect. 111(Routledge and Kegan Paul, 1968); H. Putnam's article in Dimensions of Mind, ed. S. Hook (Collier); R. Rorty's article in Review of Metaphysics, vol. 19, 1965, re- printed in Philosophy of Mind, ed. S. Hampshire (Harper and Row).

Some have argued that the theoretical reductions of science are not necessarily identifications, e.g. Jaegmon Kim in American Philosophical Quarterly, July 1966; this issue is unimportant unless one wishes to use an empirical Identity Theqry as the basis of a materialist philosophy. My interest here is only in the empirical question and I suspect that Identity Theorists should be satisfied with a theoretical reduction.

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503 MIKD, BRAIN AND IDENTITY

and under which questions of change, persistence and anni- hilation are settled. It is plain that the identity-conditions of a play differ from the identity-conditions of one copy of that play. The play does not depend for its existence on any material copy of it, for it might be memorized; but the copy cannot exist without something on which i t is copied. The .copy can be destroyed by the destruction of one material object; but the play cannot (except under special conditions). The play can be altered by the author's changing his mind; but the copy cannot be altered by this alone. These discrepancies in the two sets of identity-conditions clearly forbid the identification of, say, The Winter's Tale with any particular copy of it, even the author's original.

The question that must be considered, then, is this: are the identity-conditions of mental events and brain processes so discrepant as to forbid an Identity Theory, just as the identification of a play with a copy of i t is forbidden? It seems clear that a discrepancy sufficient to prohibit identification need not be precisely analogous to that of my example, though I am not clear as to the minimum discrepancy for ruling out identification. Of course any failure to discover a discrepancy does not entail the identification but merely removes a possible objection to i t ; and I do not want to be understood as an advocate of an Identity Theory. What follows is simply an investigation into the identity- conditions of mental events and brain processes (or, more strictly, processes of the central nervous system).

'Well! I've often seen a cat without a grin,' thought Alice; ' but a grin without a cat! It's the most curious thing I ever saw in all my life! '

Lewis Carroll: Alice i n Wonderland

Stuart Hampshire1 distinguishes two kinds of identifying principle employed by human beings in correlating particular groups of signs with particular recurrent elements in reality:

first, rules that single out elements in reality as being of the same kind, and that identify recurring kinds of thing: secondly, rules that single out one specimen of a certain kind from another, and that identify the same one as recurring or appearing again. Rules of the first type may be called principles of classification: rules of the second type rnay be calledprinciplesof individuation.

Thought and Action (Chstto and \Vindus 19(i6), p. 12.

Whenever the verbs ' classifv ' and ' individuate ' are used from now on, they should be understood as deriving their mean- ing from what is said in the above passage. A parallel with the traditional distinction between qualitative and numerical identity can immediately be seen here, a parallel that emerges more clearly when Hampshire goes on to consider the applicability of his principles to the identity of sensations (pp. 27-28) : .

To say that I felt alike, or that I experienced exactly the same sensation, on two different occasions seems to imply that there is nothing that can be truly said in description of my sensation on one occasion that cannot be truly said of my sensation on the other occasion. Plainly some restriction on the type of description is presupposed here; and this restriction is implied in the word ' sensation '. . . . We mark by ' same sensation ' or ' same situation ' the type of identity in description that is applicable. A sensation is not a type of thing, a thing that can be identified. . . . Consequently ' same ', as it occurs in ' same sensation ' or ' same situation ', does not have the same definite use as in ' same horse ' or ' same man '. The question whether two men ever had the same sensation. . . is not a determinate question with a definite sense. This would only be a real question if there was a sense of numerically the same sensation. . . corresponding to the sense of numerically the same horse. There is no principle of individuation attached to such concepts as ' situation ' or ' sensation '. We cannot intelligibly ask how many situations, or how many sensations there were. If we speak of the same situation, or the same sensation, lasting through some period of time, 'same ' could alxvays be replaced here by ' exactly similar '.

All this is in strong contrast with the following passage taken from an article by Anthony Quintonl (p. 211):

Suppose that two people, A and B, have qualitatively in-distinguishable feelings of annoyance at a high whistling noise in their immediate neighbourhood, beginning at the same time and persisting for the same period. How in these circumstances are we to justify the belief we are very strongly inclined to hold that there are two experiences going on here and not just one?

Are we in fact strongly inclined, as Quinton maintains, to hold this belief that Hampshire claims to be without determinate sense? This question can surely only be answered by bringing out the way in which the concept of identity applies to mental events. Hampshire talks of sensations, Quinton of experiences;

Article in Brain ant1 Mind,ed. J. R. Smythies (Ro~t~ledge and Kegau Paul), 1965.

505 MIND, BRAIN AND IDENTITY

this discussion will deal mainly with thoughts in the hope that what is said will normally apply to sensations and experiences as well. with the uroviso that the extension of the argument

0

should not be effecied without separate consideration of the new examples concerned.

Let i t be su~uosed for the sake of argument that we have a I I "

principle of individuation, i.e. that there is sense in Qhinton's remarks. How can we identifyingly refer, that is succeed in making a unique reference, to a particular thought? (A parti-cular thought is something the identity of which depends upon a principle of individuation as well as a principle of classification.) We cannot, apparently, secure unique reference by pointing to it qua thought, as can be done in many cases with particulars; equally we cannot immediately understand how to use the verbal demonstratives ' This thought ' and ' That thought ' even where a suitable context would make actual pointing unnecessary. Perhaps a relatively exhaustive description of the thought would suffice for ensuring uniqueness of reference? Such a description might be, " The structure of Lawrence Durrell's Alexandria Quurtet has been determined by his desire to take account of increasing scientific knowledge ". What is there about this description that will guarantee uniqueness of identifying reference of the kind required by Quinton and denied by Hampshire? So far, nothing. We have not succeeded in supplementing the principle of classification for thoughts with a principle of individuation, for our description provides no means of distinguishing this thought from that one of the same type, no means of individuating a particular thought. Yet surely there is a possible distinction between identical thoughts occurring " " at different times and places; and if there is such a possibility, surely a principle of individuation can be devised to guarantee the distinction? However, even if we admit this possibility there remains the problem, raised by Quinton, of the same thought occurring to two different people at the same time and approxi- mately the same place. What distinctions concerning identity can be drawn here? What makes Quinton want to say that if two different people are involved there must be two thoughts and not one?

The answer is fairly simple, and has indeed already been provided in the framing of the question: i t is that a particular thought cannot be identified in language except as the thought of some particular person. Unless the uniquely identifying reference to some person is made (e.g. " Jones's thought that Smith is dead " and " Brown's thought that Smith is dead "),

506 S. CANDLISH:

the thought has not the status of a particular but only of a non-particular individual. For explanation of these terms see P. F. Strawson. Indkidtcals, pp. 226-267. The status of an individual, thus defined as what can be the logical subject of a proposition, will depend on its iderltiiication by means of principles of classification, but not necessarily by means of principles of individuation, for the latter may not be relevant. The status of a particular as particular will depend on its identification by means of principles of individuation as well as principles of classification. Thus all particulars will be individuals, but not all individuals particulars. It is important to realize that with this inixed terminology, identifying something by means of principles of individuation, i.e. individuating it, guarantees its status not just as an individual but also as a particular, given that the principle of individuation is separable from the principle of classification. The notion of a particular is best illustrated by means of examples such as the river Amazon, the present Duke of Norfollc, that gatepost, this shadow, the Industrial Revolution and so on; all of which may be contrasted with what are tradi- tionally called universals, such as numbers, properties, concepts and so on.

Consideration of this answer shows what lies behind the apparent conflict between Hampshire and Quinton: that thoughts as mere individuals get their identity from principles of classification, the most definitive of which is the exhaustive description of the thoughts, these principles not being supple- mented by a principle of individuation (or, if it is preferred, the two kinds of principle here fall into one); while thoughts as particulars rather dubiously attain this status through getting their identity from a principle of individuation which involves individuating persons. It might be said that the principle of individuation for particular thoughts is simply the principle of individuation for particular people. Another example of a kind of thing with this kind of identity is a smile. Jones may smile a particular smile on a certain occasion, and others may smile many similar smiles, but that certain smile, attributed to Jones, cannot be smiled by anyone else for this would flout the conditions under which it gets its identity as a particular.

One small difficulty remains, that was exemplified in the second quotation from Hampshire. Given that we may talk of a particular thought when this has the force in use of" Jones's thought ", can we now introduce n principle of individuation nliich will enable us to identify as particulars c~ualitativelv itlentical tl~oaghts of the saine person? If not, our so-called


principle of individuation for thoughts is not a genuine individuating principle a t all, for the same personmay haveatdifferent times the same thought and if we cannot class these separate events as separate thoughts but are confined instead to treating them as different occurrences of the same thought, we have not succeeded in providing the uniqueness of reference ,required. We may, however, introduce such a principle, and its form has already been suggested: that if the same person has the same thought a t two different times, this is to count as having two qualitatively identical but numerically diverse thoughts.

A sense has been found, then, for the expression ' a particular thought '; but its use is limited, for whenever we begin to try and distinguish two qualitatively identical thoughts we find, ipso facto, that we are distinguishing two people, or two different times or situations in the life of one person. This is what leads Hampshire to say that we have no principle of individuation for sensations; and it also explains why Quinton is so concerned to distinguish between the experiences of different people. (In-cidentally, as will emerge later, this point throws some light on the question of knowledge of other minds.)

The introduction of these principles of individuation for thoughts is, of course,relatively arbitrary, and we have little use for such a device; but equally there seems to be no overwhelming reason why we should not use it, and I shall offer some examples where such a principle might have a use. As a general point, however, the introduction seems not only arbitrary but pointless. It is worth noticing here that the pointlessness is not solely due to the fact that there is no immediately clear place in the concept of thought for the concept of spatial location, for certain obviously spatial individuals also typically lack a principle of individuation.

For example, the Cheshire Cat can grin the same grin on a number of occasions, think the same thing on a number of occasions, and say the same thing at different times and places. Here there does not seem to be much point in introducing a principle of individuation.

There might be more point in individuating illnesses, though this could still be comfortably avoided by speaking of bouts of illness; and there might be point, too, in individuating qualitatively identical pains. We might, for instance, stipulate that the same kind of pain occurring on two different occasions was to count as two particular pains if it could be established that the causes of the pain were different in each case. There is apparently some choice, too, over whether a constantly recurring pain should count as one throbbing pain or as the same pain coming

508 S. CANDLISH:

again and again; provided we are clear about the facts our choice of terminology here matters little. We might be in- fluenced in the choice, if i t were ever made, by factors like the amount of the temporal gap between occurrences of the throb, and as in the previous case by consideration of causes: e.g. we might think of throbbing pains as generally associated with minor ailments, whereas a single pain that recurred at regular intervals might be associated with something seriously wrong. Plainly, here a distinction would have a point that was at least psychological in its effects; but normally there are no precise rules to be observed in these cases; and while we perhaps have a choice whether to frame precise rules or not, we usually do not exercise the choice because there is no special purpose to be fulfilled by its exercise.

A picture has been built up of the place of the concept of identity in the concepts of thought and sensation, which gives in outline what have been called the identity-conditions of instances of these concepts. What must be considered now is how the concept of identity applies to processes in general, and to brain processes in particular. Can any parallels be discovered in the identity-conditions of thoughts and brain processes; and if not, what are the consequences for an Identity Thesis? Further, are there any less controversial identity-questions with which an Identity Thesis can profitably be compared?

In fact, the way in which the concept of identity fits into the concepts of thought and sensation is remarkably-some nlay think, distressingly-similar to the way i t fits into the concepts of various processes. Processes can typically (Ido not say always) be described in terms which supply a principle of classification but not of individuation. To take a simple example, one can describe the process of boiling an egg in some such way as this: an unbroken egg is immersed in boiling water for not less than three and not more than six niinutes, at a normal atmospheric pressure. This description suffices to classify the process of egg-boiling and to separate i t from manufacturing processes and from omelette-making. However, i t does not individuate this boiling of an egg from that one; or in other words, while the process of egg-boiling may be an individual, as identified through this description, it is not a particular. How c m we amend the principle so that we can identify through it a particular


l~oiling of an egg? Olily through supplementing it with a principle that will enable us to identify particular eggs, or perhaps a particular volume of water. or container.

i t may be suggested here' that a particular process may be identified by giving its spatio-temporal location, without any reference to anything involved in the process; and there is a parallel objection to the conditions which i t has been urged are necessary to the identification of a particular thought, the objection that such a thought could be identified as the thought had in a certain place at a certain time. This objection may be admitted for, as Strawson points out (op. cit. p. 55), i t has little force. For the identifying descriptions to be admitted as such i t is necessarv that someone or other should have been able to

J

give an independent identification of the material thing(s) associated with the process, and of the owner of the thought. More-over, the possibility of giving spatio-temporal locations depends upon implicit reference to material things, and any check of the identification involves locating and examining material things (or persons) in identifying the process (or thought) with the particular identity of which we are concerned.

There are several ways of indicating the kind of identity- dependence which processes have on the things they involve. It might be said, as was said about thoughts, that processes only get their status as particulars rather dubiously, in virtue of the non-dubious status as particulars of the material things which processes involve; or it might be said that if we cared to distinguish qualitative from numerical identity in the case of processes, as with thoughts, the distinction could only be accomplished through applying the same distinction to the things involved in the processes or which have the thoughts; or it might be said, in the way that Hampshire does, that the concept of numerical identitv has no force over and above that of auali- tative identity with processes, as with thoughts; or we might be tempted to distinguish between an individual process (non- particular) and its particular instances, as perhaps between an individual t h o u ~ h t and its articular occurrences to various

0

people or the same person at different times; similarly, i t might be tempting to invoke a typeltoken distinction. All these are ways of pointing to the peculiar place of identity in the concept of a process, a place quite strikingly similar to its place in the concept of a thought.

Do theie points mavde about the identity-conditions of typical processes still hold when individual kinds of processes are dealt with? In particular, do they hold for brain processes? Putting

510 S. CANDLISH:

aside for the time being the actual technical difficulties of ideati- fying even individual (let alone particular) brain processes,l i t appears that these general points do hold good in this individual case.

If we are to give sense to the idea of identifying particular brain processes as well as individual ones, i.e. to the numerical identity of brain processes as well as their qualitative identity, we are faced with exactlv the same difficulties over articular identification: that such an identification can only be performed by identifying a particular brain, just as in locating and identifying a particular manufacturing process, location and identification of the factorv and machines involved are necessarilv performed. Again, we may be given the spatio-temporal location of the brain process as a means of identifying it; but this has no more effect on the general thesis iust outlined than a similar point had on the ge;eral thesis co&erning the identification of typical processes and of thoughts. In a way, identifying a particular brain process is ipso facto identifying a particular brain (which, normally, will ipso facto be identifying a person, animal, etc.), and distinguishing as separate particulars two qualitatively identical brain processes will be either distinguishing two different brains or two different times in the history of one brain; just as the identification of a particular thought is ipso facto the identification of a person (Jones's thought), and the distinction as separate particulars of two qualitatively identical thoughts is the distinction between two people or two periods in the history of one person. If the status of a brain process as a separately identifiable particular is objectionable, then equally a thought's having this status is objectionable. Purther, if this doubt is acted upon, and we refuse to admit brain processes and thoughts as particulars, allowing them to appear in discourse only as non-particulars, it remains impossible to provide a means of identification of the occurrence of an individual brain process or thought. or a means of reidentification at its recurrence. which " , does not involve any reference a t all to brains or people.

It is worth remarking here that Professor Armstrong makes the admittedly difficult task he sets himself in A Materialist Theory of the Mind rather more difficult than is necessary by assuming that

. . . mental states are incapable of independent existence

. . . [But] brain states or processes seem to be things that could be conceived.to exist independently of anything else.

1 Cf. A. R. Luria, Human Brain and Psychological Processes (Harper and Row, 1965), part I.

MIND, BRAIN AND IDENTITY 511

They do not even require a brniri, for we ooulcl conceive tl1e111 as, e.g. patterns of electrical discharge in space (p. 76).

Armstrong fails to see that there could be a question here of whether a process that occurs independently of a brain could be a brain process. This is not just a verbal point, since i t is not the case that everything has its identity and nature totally independently of its surroundings. There are obvious examples of this, like actions, but it is not yet generally recognized that even many of the entities of science are logically related to the surroundings and circumstances in which they 0ccur.l

Although the identity-conditions of thoughts and brain-processes are so similar, there is a point a t which a discrepancy seems to arise, namely, that we can succeed in identifying a brain process (individual or particular) in a way in which we can never succeed in identifying a thought, by simply pointing. If this is correct, i t creates an obvious difficulty for an Identity Thesis, the same difficulty that has been a standard objection to such a thesis in the past: that to say that brain processes are spatially located in the head is to utter a plain truth whereas to say that thoughts are spatially located in the head is to utter n~nsense .~

Now as pointing a t anything at all requires a context for the gesture to be understood, and as there are invisible and intangible processes occurring in space (e.g. in the germination of a seed) which cannot clearly be pointed to without the provision of a very sophisticated context, it seems that the real force of this objection does lie in the issue, not of pointing, but of spatial location. It is important to notice that i t is not the mere property-discrepancy which is important here. If it were then the objection would be relying on the Principle of Indiscernibility of Identicals. But the rationale of this whole discussion is that we should be free of such generalizations concerning identity-questions, and hence the problem posed is specifically that of the identification of phenomena that are not clearly spatial with those which are.3

Cf. N. R. Hanson, Patterns of Discovery (Cambridge,1965),ch. 111. Cf. J. Beloff's article in Smythies, op. cit.: R. B. Brandt's article in

Hook, op. cit.; R. C. Coburn's article in Journal of Philosophy, 60, 1963; Malcolm's synopsis in the same place and his article in Dialogue, vol. 3, 1964; S. C. Pepper's article in Hook, op. cit.; A. Quinton's article in Smythies, op. cit.; and J. Shaffer's articles in Journal of Philosophy, vols. 58, 1961 and 60, 1963 and American Philosophical Quarterly, vol. 2, 1965.

3 It will be noticed here' that ' identify ' has been used in two different senses, namely, that of ' identify with ' and that of ' identify as '. The two senses are connected, as can be seen by consulting S. Shoemaker, Self-Knowledge and Self-Identity (Cornell University Press), ch. 5 sect.11 and p. 259; and nothing turns on the apparent ambiguity.

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It is important also to realize that there is at least a modicum of sense in the idea that a particular thought has spatial location; and this is shown by the fact that a particular thought can be identified as ' the thought occurring in a certain place at a certain time '. On this basis, combined with certain analogous and already accepted theoretical ,reductions of phenomena that are not clearly spatial to those that are, one could argue, as Kim (op. cit.) has done very successfully, that this standard objection has no force. For one who upholds the objection must be able to show that the particular to which the thought or other mental event is attributed is itself not spatially located, and it is not clear that even a Cartesian dualist would wish to maintain this, even if he thought the soul did not occupy space.

An interesting sidelight is cast here upon another argument against an Identity Thesis, put forward by Baier,l that brain processes are publicly accessible whereas thoughts and sensations are private, so that an identification is impossible. Among the five criteria of privacy that Baier lists, criteria which mental events are supposed to satisfy but brain processes are not, are necessary ownership and necessary unshareability. These characteristics apparently, whether combined or not with the others that Baier mentions, are held to be incompatible with the publicity that would be required of mental events should they be identified with brain processes. Now if the previous description of the identity-conditions of thoughts and brain processes is correct, it is clear that Baier's argument is by no means as cogent as it initially appears, for the characteristics mentioned as com-prising in part the so-called privacy of thoughts are equally characteristics of brain processes. The supposed necessary ownership and necessary unshareability of thoughts, which are presumed by Baier to be characteristics solely of the mental, are simply conditions of their identification as particulars. If they are identified only as individuals, i .e. only according to a principle of classification and not of individuation, then necessary ownership and unshareability are no longer characteristic of mental events in any straightforward sense. And these same points are true of brain processes: if they are identified as particulars, they are just as necessarily owned and unshareable as any thought, for they can be identified only as processes occurring in particular brains, just as a particular thought can be identified only as the thought of a particular person; while if identified merely as non-particular individuals, a principle of classification

1 K. Baier, article in Australasian Journal of Philosophy, vol. 40, 1962, p. 60.

513 MIND,BRAIN AND IDENTITY

alone will suffice for identification and necessary ownership and unshareability are no longer straightforwardly characteristic of brain processes either. If we allow talk of particular thoughts and particular processes, in the sense given above to particularity, then two brains can no more share the same particular process than two people can share the same particular thought; while if the right to speak of particulars is denied here, sharing and lack of necessary ownership are no more of a problem with thoughts than with brain processes. In the latter case. both thoughts " and brain processes can be said to exist unowned by any particular person or brain, although they could not be said to exist even as non-particulars if no person or brain had ever exemplified them. This denial could be virtuallv self-defeating in the case of thoughts, but this problem couid be avoidedv by careful locution and reference to intentions. All that Baier has succeeded in doing with his presentation of thoughts and sensations as necessarilv owned and necessarilv unshareable is to outline their identiti-conditions in such a misleading and distorted way as to suggest that people are the dwelling-places of Cartesian egos. All that these two points really indicate is idhe identifiability-dependence of thoughts and sensations upon people; and identifiability-dependence is not characteristic of mental events at all, for it is equally present in the identification of brain processes, manufacturing processes, gaits, shadows (perhaps), grins and many other kinds of thing.l There is nothing meta- physically strange about this. It is, perhaps, no accident that we have in English the phrase ' thought process '.

Before abandoning this topic of identification and the identity- conditions of thoughts and brain processes, it may be of use to apply the same techniques of enquiry to an undisputed identity statement (or at least reduction) made in the course of the develop- ment of the Kinetic Theory of Matter. One example only will be discussed here, but i t is one of many: the identification of temperature with mean molecular kinetic energy. This, perhaps, is a fairly typical example of the identification of macro-phenomena with micro-phenomena, another example of which is the identification of light with electro-magnetic radiation. One philosopher has said " . . .every argument for and against identification would apply equally in the mind-body case and in

1 Cf.Wittgenstein, Philosophical Investigations I, paras. 248-253.

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the light-electromagnetisni case " . I . Whether one agrees with such a remark or not, an examination of the place of identity in these scientific concepts may throw light on what motivates its utterance.

Professor C. N. Hinshelwood has said in a recent account of modern physical chemistry:

The statements contained in the equations p = 113 (mnii2) and p V = RT constitute the simplest possible illustrations of the thesis, established in the course of the nineteenth century, that heat in general is a mode of motion. Since, as in the experiment where Joule warmed up water by the churning action transmitted from falling weights, mechanical energy of a mass is quantitatively convertibleintoheat, andsince all attempts to account for such phenomena in terms of a special kind of caloric fluid prove to be sterile, the identification of heat with the invisible chaotic motion of the molecules is compelling.

He then offers a brief explanation of the identification: Mechanical energy becomes apparent when the motions of the invisible parts are so coordinated as to give rise to perceptible motion of the group: it is transformed into heat when the coordination is destroyed and the motion is no longer dis- cernible by any of the senses save that which permits the appre- ciation of warmth. From the point of view of the individual molecule, nothing has occurred when mechanical energy has become heat, and the quantitative equivalence of heat and energy is simply a special example of the conservation of energy. This equivalence is asserted as an empirical principle in the First Law of Therm~dgnamics."~

Now as quantity of heat is not itself a process, there may be little point in exploring possible analogies with the kinds of identity we have considered so far; however, as change in quantity of heat is a process, and so is change in quantity of mean molecular kinetic energy, an enquiry into the identification of these phenomena with each other (it is almost impossible to avoid incoherence like this when speaking in the material mode of identity), and into their identity-conditions may be hoped to bear fruit. On the face of it, the identification of temperature change with change in molecular energy is wildly paradoxical; their properties are so discrepant that the assertion of identity looks nonsensical. It is only in the light of the explanatory theory adumbrated by Hinshelwood that the identification

if we attempt to suspend our acceptance

1 H. Putnam, in Hook (op. cit.), p. 157. Cf. also my note 2. a C. N. Hinshelwood, The Xtructure of Physical Chemistry (Oxford, 1951).

;, begins to take on sense


of this theory and look at the matter with an innocent eye, the property-discrepancies take on such exaggerated proportions as to render the identification completely unacceptable, and we may begin to wonder if an Identity Thesis of mind and brain could be any more ~?aradoxical.

What, then, is the place of the concept of identity in the concept of temperature change? What is going to count as the same change and what is not? As was found before with thoughts and brain processes, there is the possibility of exercise of a certain measure of choice. For certain purposes we may be prepared to count as one change one of 5"C, whether this is an increase or decrease and whatever i t occurs in or to. In other cases we may stipulate that the initial and final temperature must be known: or ;imply that the direction of the chaige is relevant to identity: questions; or that what it is the temperature of which has changed will weigh with us in determining what is to count as the same change. Not only are there these points which may be taken into account, but again Hampshire's original remark concerning the identification of sensations seems to apply: that there is no distinction of numerical from qualitative identity here; or, in our less dogmatic form, that we do not usually require the distinction to be made. If a description of a temperature change is given in some such way as this: ' a rise of 6°K from 305" over a period of two hours '. this description will serve to

A

identify all changes falling under it, i.e. will serve as a principle of classification. The change will then be merely a non-particular individual, for there may be many particular changes which satisfy the description and thus count as the same change. But the description does not identify a particular temperature change, for the possibility of such an identification rests on a principle of individuation which involves the identification as a particular of the material the temperature of which has changed, or something else also closely connected with the change such as the container of the material. (' Material ' here is used in the general sense in which, say, a volume of gas can be material.) If it is required to identify a certain temperature change as a particular, this can be accomplished only by providing a means of distinguishing in experience the particular thing the temperature of which has changed, or some other particular thing closely connected with the identity of the former. Ultimately, the possibility of demonstrative identification, of pointing, may be invoked in order to secure the unambiguous identification.

Again, there are many ways of putting this point, for example : temperature changes can only get their change in identity-status

froill non-particulars to particulars in virtue of the paradigrii status as particulars of the material things involved in the changes; or, following Hampshire somewhat dogmatically, for temperature changes there is only a principle of classification and not of individuation, and there is thus no sense in ascribing numerical identity to them (or the two principles, and hence the two kinds of identity, fall into one with this concept); or the distinction betweeen numerical and qualitative identity is viable for temperature changes only on the basis of an undisputed distinction of this type for material things; or equally, that temperature changes as particulars are necessarily owned and necessarily unshareable, though not owned and unshareable in the same way when treated only as non-particular individuals; or perhaps that there is a distinction between a temperature change and its instances, or between the type and its tokens.

It is possible to envisage circumstances in which we might want to distinguish and identify temperature changes as particulars. For instance, a doctor, on finding that my body temperature has risen by 2"F, may say that this change is a bad sign without thereby implying that all rises of 2°F are bad signs whatever they occur in or to, nor even that it is a bad sign for all people; for someone whose disease-symptoms are unlike mine the change may be neutral, and it may be neutral for me too on a different occasion. Of course it is always possible to eta in non-particular status for this change by detailed specification of circumstances, but in certain cases this may be difficult and tedious.

It is possible, too, though a little more difficult, to imagine situations in which we might want to identify thoughts as particulars: an official, high in the ranks of the all-powerful governing Party, presiding a t the trial of a lesser citizen, may judge to be seditious the thought which he, the defendant, foolishly disclosed to an agent of the secret police, e.g. that the Party should alter its economic policy to one of planned growth in the face of increasing inflation; in doing this he may not imply that should he (the official) have this thought, the thought would be seditious then also-for whereas before it was criticism of the Party, in his case it would be constructive re-interpretation of accepted doctrine. Further, that official might remember having that thought himself while a young man, though he of course was too clever to admit it-that's why he was presiding a t the trial; and he might agree that his first thought had been seditious while his second had not. Moreover, one does not have to be a relativist in morals to suppose that this official might


even be right. Again we can refuse particular status to thoughts a t the cost of an increasing complexity of the principle of classification: but this mav not be convenient. and we could admit them td. such a stat&. Another way in which we might be prepared to accord the identity-status of a particular to a thought of a person is in the case \.here the conditions stimulating that thought are different for different people. For instance, one person may feel lazy while another reads the weather forecast both may think ' Let's stay in today ', and we may be prepared to stipulate that here are two qualitatively identical but numerically different thoughts, Jones's and Smith's. Identification as particulars is not ,required in these cases, but its possibility seems to be of the same kind as the possibility of identification as particulars of temperature changes and of brain processes. Normally, the possibility is not acted upon.

What, now, of mean molecular kinetic energy? Obviously for many purposes this is a special case compared with those that we have examined so far for i t is a rather specialized scientific concept, whereas until now only a few very ordinary examples have been studied; further, micro-phenomena are now involved. Despite these differences, however, the place of identity in the concept of energy change seems remarkably similar to its place in the concepts of thought, brain processes and temperature change. To reiterate all the ways of looking at the identity of energy changes a t this point would be unnecessarily tedious; it suffices to point out that the appropriate substitutions in the discussion of the identity of temperature changes will show that there is a quite definite parallel here for the identity of energy changes with the identities of those concepts dealt with so far.

MThat can be drawn in the way of conclusions from this discussion? First, i t is quite clear that a conclusive refutation of any form of Identity Thesis could have been based on a major discrepancy of identity-conditions of mental events and brain processes; but that as there is no such discrepancy such an objection is not forthcoming. Secondly, certain actual objections to an Identity Thesis have been countered en, route. Thirdly, a suggestive analogy with an established scientific advance has been investigated. AH' these points indicate that the idea of a scientific Identity Thesis in the form of a theoretical reduction may make sense. What is required now is a further investigation of the conditions under which such reductions have been effected

518 S. CANDLISH :MIND,BRAIN AND IDENTITY

in the past, with a view to establishing whether or not the pro- jected reduction of the Identity Theorists would conform to these conditions, and if not, whether nonconformity would matter.

One final point is worth making (and I am grateful to Professor Ryle for helping me to clarify my thoughts here). If, in this or some other investigation, a conclusive logical objection to an Identity Theory had been established, i t would be extremely tempting to deny the truth of an Identity Theory and in so doing to be committed to saying that brain processes and mental events are different kinds of thing. I would conjecture that something like this temptation was at work on Professor Armstrong when he suggested, on page 14 of A Materialist Theory of the Mind, that anyone who thinks at all extensively about problems of mind and matter must hold some version of one of a limited number of " theories of mind ". (The alternative to this seems to be " intellectual corruption ".)

However, if some conclusive objection were established (show- ing, e.g. that there could be neither any bridging concept supplying an answer to the question " The same what? " nor any scientific theory within which the identity assertion could take on sense) then of course the identity assertion is shown to be not merely false but nonsensical (non-sense). If i t is nonsensical then so is its denial, the counter-assertion of difference. To say this is not to prohibit this use of negation; but i t is to point out that it is ill- advised. It " makes the difference between the meanings look too slight. (It is like saying: numerals are actual, and numbers non-actual, objects.) An unsuitable type of expression is a sure means of remaining in a state of confusion." (Wittgenstein, op. cit. I , para. 339). The standard examples of empirically- established identifications used in the discussions of this topic, like Hesperus and Phosphorus, add further to the confusion a t this point, tempting us to think that philosophy is a quasi-empirical discipline. Those who reject an Identity Theory must be careful how they do it; but in doing it they are not committed to some form of dualism.1

University of Western Australia

1For an alternative see Wittgenstein, Bette1 (Blackwell, 1967)§$603-613.

mind, brain and identity

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