Published in Synthese 22 (1971) 295-312.
SOME CRUCIAL ISSUES OF MIND-BODY MONISM
My remarks are made within a framework of assumptions or presuppositions that may be best characterized as those of a scientifically oriented critical realism, and a tentative (physicalistic) reductionism. Since this position has been amply argued for in numerous publications (e.g., by R. Carnap; P. Oppenheim and H. Putnam; J. J. C. Smart; D. M. Armstrong; myself; and many others) I shall review now very succinctly only the points relevant for the important qualifications which differentiate my own views from those of the others.
Having originally taken my cues from the (by now 'classical') critical realism of the early Moritz Schlick and the later Bertrand Russell, as well as having favored the somewhat similar views of the American monistic 'naturalists' (especially R. W. Sellars, but also C. A. Strong and Durant Drake), I assume that there is -- epistemologically -- an important distinction to be made between the data of immediate experience and the world of 'things-in-themselves'. But in radical disagreement with the agnostic doctrine of Kant (and in complete agreement with Schlick and Russell) I consider the things-in-themselves knowable. And I hasten to add that such scientific knowledge as we possess of them, and keep expanding is 'structural', i.e., it is knowledge by description (in B. Russell's sense, recently explicated more formally by R. B. Braithwaite, R. Carnap, and G. Maxwell with the help of the Ramsey-sentence approach). While very few of the deeprooted beliefs of commonsense -- I as for example those philosophically formulated in 'direct realism' -- survive epistemological and scientific criticism, some of the basic tenets of commonsense remain (relatively) unscathed. If the well known disastrous slide into phenomenalism (or instrumentalism), and ultimately into a solipsism of the present moment is to be avoided, Berkeley's "esse est percipi" must be rejected from the start, and the existence (independently of perception) of the 'external world' assumed.
The much discussed quantum-mechanical, partial dependence of the observed or measured situation upon the act of observation or measurement can be safely disregarded in the present context. The influence of observation on observed objects maintained by a majority of present-day physicists is in any case negligible in regard to macro-objects. ("It does not hurt the moon to look at it," even if electrons do get a 'kick' out of being looked at.) As to whether the finer details of neural processes (e.g., in the synapses of the central nervous system) require considerations of complementarity and indeterminacy is, however, a relevant question in regard to the identification (individuation) of neural events. Moreover it seems quite questionable as to whether the 'subjectivistic' interpretation of quantum mechanics is really called for.
For our purposes, and with some simplification, we can regard the assumptions of critical realism as among the premises of a hypothetico-deductive system. But just as the theories of the factual sciences generally, so also even these frame assumptions must be testable (in principle, and no matter how indirectly) by the data of immediate observation. This minimum of empiricism is in any case indispensable if the obvious fundamental difference of pure logic and mathematics from factual knowledge is to be properly understood.
One other assumption of commonsense survives: It is the identity of mental states, events or processes (sensations, thoughts, intentions, desires, volitions, moods, sentiments, etc.) referred to by persons who 'have' them and other persons who come to know about them on the basis of behavioral (including, of course, linguistic) or neurophysiological evidence. To illustrate: My doctor knows that he is causing me the experience of a pain when he lances an abscess on my arm; and I feel that pain and can report (or 'avow') it. This much seems clear, and is indeed insisted upon by the philosophers of ordinary language (Wittgenstein, Austin, Strawson, Malcolm, et al.). Despite their opposition to the idea of a private language, (or perhaps because of that opposition!) they do not countenance the notion that the word 'pain' has different meanings in first person experiential reports and in ascriptions to other persons (or by other persons to me).
This point, however, requires a crucially important re-examination. I maintain (again in agreement with Russell) that without analogical conception and reasoning by analogy, the identity (in the sense of synonymy) of first-person (self-ascribed, reported, avowed, or otherwise indicated) experience with experience ascribed to that (first) person by other persons can be understood only in the very different sense made widely familiar by the (logical) behaviorists, physicalists, or the Australian materialists. This other sense is quite clear: it retains essentially the point of view of the 'psychology of the other one'. Anxious to make psychology in honest natural science, the behaviorists -- from Watson to Skinner --have consistently dealt with mental phenomena within the frame of an intersubjective account of the world. This trend of thought began with the crude identification of mind with behavior (J. B. Watson, E. A. Singer), and became more sophisticated in the views of R. Carnap, G. Ryle, and B. F. Skinner. These two philosophers and that brilliant psychologist attempted (in different ways) to show that assumptions of a publicly (intersubjectively) inaccessible mental life are either outright meaningless (though pictorially and/or emotionally significant) or, in any case, redundant for the aims of scientific description and explanation of human behavior.
There are two reasons -- and I trust not merely argumenta ad hominem -- which have for a long time convinced me of the indispensability of a subjectivistically understood conception of immediate (first person) experience. There is, first, the epistemic primacy of the data of immediate experience. Lest I be accused of attempting to resurrect the doctrine of 'incorrigible' sense-data-statements, let me say right now that the empiricism to which I subscribe, requires neither infallible 'protocol' or 'basic' statements; nor does it assume an atomistic ('pointillistic') structure of the phenomenally given. Moreover I would not only admit, but insist that sense-data as traditionally understood are the products (really 'destructs') of a very special sort of analysis. Ordinary, normal adult direct experience is perhaps best described as the life-world ('Lebenswelt') of the phenomenologists and existentialists. That is to say that ordinary immediate experience is suffused with interpretation, remnants of memory, expectations, associations, etc. But even if by a wrench of abstraction we succeed in stripping off this 'overlay', what remains are I hardly ever elementary ('atomic') sense data but Gestalten (i.e., patterns, configurations, etc.). Experimental psychophysiology has for some time suggested that the much discussed isomorphism holds between these Gestalten and certain global features of cerebral processes. (I shall return to this important point later.)
In the pursuit of a logico-epistemological reconstruction of our knowledge-claims regarding the 'external' or 'physical' world we are -- in the last analysis -- driven back to the phenomenally given as the ultimate testing ground. Consider such confirmations as, for example, of astrophysical hypotheses by means of telescopic, spectroscopic or other observations. Feyerabend's contentions to the contrary not withstanding, the astronomer ultimately has got to see (or if he is blind -- to hear or touch) something. Of course I admit that what is thus sensed would make no sense without some presupposed theory (as e.g., of optics, photography or the like). But those theories in turn have been (let us assume successfully) tested by previous observations. 'Incorrigibility' is not required. Even basic statements may have to be revised in the light of further observations -- and theories.
In this age of electronic computers, robots, etc., it has been argued that the human observer and his immediate experience could be replaced by machines that do the 'observing'. The reply to this objection is quite simple: How would we human beings ascertain the reliability of observation-machines; and is it not epistemology for human beings (and neither for gods nor machines) that we are trying to work out?!
The second point (that again I do not consider an argumentum ad hominem -- let alone a sentimental and fallacious piece of reasoning) is that the very understanding of moral imperatives requires indispensably references -- literally -- to direct experience. "Thou shalt not wantonly inflict pains on humans or animals" will serve as a simple example. The word 'pain' here has a surplus (factual -- not purely emotivel) meaning over and above the one that radical behaviorists, physicalists or materialists countenance. I trust that I am not taken to be moralizing in this context. What I am saying is that there is a cognitive presupposition in ethical imperatives. Even someone who holds a purely non-cognitive ('emotivist') position in moral philosophy can -- I hope -- understand and igree.
Having been a member of the Vienna Circle (ca. 1924-1930) I realize that logical positivists (empiricists) or radical physicalists will shake their collective heads and accuse me of apostasy. But I have been a renegade from that movement and became a critical (or 'hypercritical') realist at least thirty years ago. Along with others I have tried to liberalize the empiricist meaning criterion in a manner that still excludes the 'pernicious' transcendence of certain types of metaphysics and theology; and yet allows for analogical conception and inference. If a theologian wishes to construe his beliefs in this manner, I will not tell him that what he is asserting is meaningless. I shall merely ask him by what sort of reasons he can justify his beliefs. 'Far-out' scientific hypotheses, such as those of current nuclear theory or of cosmology are merely 'precariously' transcendent. Hence I think that empiricists should consider theological (or metaphysical) assertions as meaningful provided they are at least incompletely and indirectly testable.
Considered superficially, analogical conception and inference of other minds appear to share the features of 'perniciously' transcendent metaphysics and theology. To use the well known Peirce-James formulation, there seems to be "no difference that makes a difference" in regard to all conceivable evidence. But I submit that our "private", "privileged" access (each must speak for himself in this matter) to our own immediate experience is a cognitive matter. The arguments of the Wittgensteinians, (especially of Norman Malcolm) are utterly implausible to me. Introspective reports or avowals are either true or false. (I have already admitted that they are not incorrigible. They may conflict with other basic statements; with background knowledge or well established theories.) Reference to one's own immediate experience is the (epistemological!) prototype of all designations of objects, properties or relations by the words of our language. Never mind how we come to use language. Very likely, reinforcement along with the existent ('innate') set of our (brain-mind) capacities accounts for that. Carnap was historically the first (anticipating both Ryle and Skinner) to point out how the use of introspective phrases (e.g., "I am glad", "I am tired", "I am afraid", "I hope...", "I am thinking of...", etc., etc.) is acquired; i.e., how the child learns, in the context of environmental circumstances, 'taught' by his elders, the uses of those subjective expressions. Of course the physicalists are right in regarding avowals as caused by central states. But to the extent that whatever human beings do or say is in principle open to causal analysis (within the possible limits implied by quantum mechanical indeterminacy), this is entirely compatible with a semiotic account (i.e., by syntax, semantics and pragmatics). This renders it possible to apply the meta-concepts of designation (representation) and of truth and falsity. In opposition to many of the Oxford linguistic philosophers (and also to Malcolm) I think it makes perfectly good sense to say 'I know that I have a pain', 'I know that I am glad', etc. But if the finesses of lexicography should speak against such uses of 'I know that...', I shall not be adamant on this point, and simply choose some other locution.
As I see it, the Neo-Wittgensteinian approach to the notorious vexations of the 'other minds' problems is still positivistic. The "beetle in the box" is just as ascertainable as the brain in the skull. But, I admit, the ascertainment of the "raw feels" (E. C. Tolman's term for immediate awareness or the phenomenal qualities) cannot be achieved in the simple manner of independently verifying the conclusion of an analogical inference. Obviously this has been the bugbear of the positivists. For similar reasons statements about the historical past should have caused them the same sort of misgivings, but strangely enough, hardly anything of the sort appears in the positivistic literature.
From the point of view of the liberalized criterion of factual meaningfulness we don't have to restrict the meaning of mental state ascriptions to the behavioral 'criteria'. The criteria of which the Neo-Wittgensteiniam speak are allegedly quite different from symptoms. Nor are they to be understood as logically equivalent to, or entailing, the ascriptions in question. They can serve as (empirically?) necessary and sufficient conditions of those ascriptions only under 'normal' circumstances. Perhaps this can be accepted as a fairly adequate analysis of the way we actually ascribe -- in ordinary situations and in terms of the commonly used language -- mental states to other persons. But is there then really that essential difference between (fairly reliable) symptoms and criteria?
For the consistent physicalists, as well as those behaviorists who at least admit that there are central states (i.e., who do not insist on the 'black box' or 'empty organism' outlook) peripheral behavior, including linguistic utterances, facial expressions, etc., serves as a probabilistic indicator of central states induced by stimuli and/or apt to (causally) produce overt responses.
Quite generally, and especially ever since the developments in pure semantics (Tarski, Carnap, et al.) it is now quite legitimate and simple to distinguish the truth conditions from the confirming evidence of a given knowledge-claim. The ascription of mental states, no matter (for the present purpose) whether understood phenomenally or in terms of brain states, is clearly and radically different from statements about the behavioral evidence. Only in the case of first person direct observation (phenomenal, experiential) statements is it plausible to identify their truth conditions with their confirming evidence. If the term 'self-evident' had not suffered traditionally so much from misuses and ambiguities, I would not hesitate to characterize statements about the phenomenally given as self-evident.
Along with other proponents of the mind-brain identity thesis, I have never asserted an identity of mental states with actual or possible peripheral behavior. It should be understood without elaboration that I also repudiate as fallacious the identification of mental qualities with aspects ot the stimuli. Obviously a color sensation, for example, is not identical with the radiation (of a certain intensity and frequency-pattern) that elicits that sensation. And, as indicated above, I also reject the phenomenalistic identification of physical objects with complexes of "elements" (Mach) of direct perception or configurations of sensation. What in more modern parlance is termed the 'translatability thesis' of physical into phenomenal language is untenable. If the errors of these types of reductionism are to be eliminated, then all the relationships mentioned, far from being identities, had better be viewed as lawful (causal) relationships between distinguishable states or events.
There is, however, one type of identification that recommends itself to our favorable attention. This is the 'reduction' of one sort of entity to another as it occurs in the context of scientific explanation. This sort of reductive identification is often (but not always, or necessarily) a macro-micro reduction. Much used examples are the kinetic theory of heat; the 'electron-gas' theory of electric currents; the identification of table-salt with sodium chloride; of genes with DNA helical molecules; of (short term) memory traces with reverberating neural circuits; etc., etc. The identification of gravitational fields with a Riemannian (i.e., non-Euclidean) structure of space-time in the general theory of relativity provides an example in which no micro-reduction is utilized. As I have emphatically pointed out in previous publications, these identifications -- i.e., the ascertainment of such reductive identities are empirical in nature. It requires empirical evidence to substantiate them. They are thus fundamentally different from identities in logic or pure mathematics.
As a first approximation in the logical reconstruction of scientific explanation this way of analyzing theoretical reductions still seems to me plausible and fruitful. But taking into account the forceful arguments of P. K. Feverabend, a more adequate and precise way of explicating those reductions would be in terms of replacement or supplantation. This is required wherever the reducing theory is logically inconsistent with the reduced theories or empirical laws. In that case we do not have identities but replacement by 'successor concepts'. But since, against Feyerabend, I maintain that the successor concepts coincide in many cases at least for a certain range of the relevant variables (and approximately) with the replaced original concepts, I shall allow myself for our purposes the simpler locutions of 'identity' and 'identification'.
Physical theories that have attained a fairly high degree of completeness characteristically provide the premises for the derivation of empirical laws. Most importantly, these empirical laws include statements about the functioning of pertinent measuring instruments, such as e.g., thermometers, ammeters, photometers, etc. Thus the expansion of the thermometric substance in a thermometer is derivable (at least with very high probability) from the kinetic theory of heat (in statistical-molecular mechanics). This still does not render the equivalence of thermometrically measured temperature with the average kinetic energy a matter of analytic synonymy. First of all the postulates of the micro-theory that furnishes the premises are synthetic and empirical. Secondly, the simple relation between thermometric indications and the corresponding set of micro-conditions is part of the confirming evidence of the theory. Redefining 'temperature' in terms of the micro-theory can and has been done, but this sort of conventionalistic device merely conceals the empirical character of the 'bridge-law' which certainly cannot be denied, especially if 'classical' ('phcnomenological') thermodynamics is compared with statistical mechanics.
Bridge laws or correspondence rules are in any case indispensable if a scientific theory is to be understood as an empirically testable set of postulates. Just where we place the 'bridge-heads', i.e., the concepts in the theoretical network and the observables is to some extent a matter of decision, and depends mainly on the aims of clarification and logical reconstruction. Thus there is, for example, some leeway as to what should be selected as the observables in the Ramsey-sentence approach.
I admit that if a given physical theory has achieved the identifications, reductions, or replacements, then one is tempted to think that there is no need for bridge laws (or nomological danglers) because the theory is then -- in a sense(!) -- complete. This, however, is an illusion. The 'anchoring' of a theory in data of experience is precisely what distinguishes physics from pure mathematics.
I shall now try to show that the 'nomological danglers' can be understood in a way that is entirely unobjectionable. They do not violate any principle of parsimony (often referred to as 'Occam's razor'). Of course I agree that parsimony in the sense of factual simplicity is one of the guiding principles of scientific theorizing. According to Newton's first regula philosopliandi we should not assume more causes than are necessary for the explanation of given phenomena. But in the case of the mind-body problem whatever parsimony or simplicity can be achieved, should result from a proper epistemological analysis of the differences and the relations between physical and psychological concepts. In other words, parsimony should be achieved as a by-product of a clarification rather than from a wilful application of Occam's razor.
The first thing to do then is to reflect on the differences between the concepts of the physical sciences and the concepts that designate immediately the phenomenally given events and their qualities and relations. To put it very briefly: the concepts of the physical sciences are invariant with respect to the different sense modalities in which they may be (ostensively) 'anchored'. To illustrate: Although it would be more difficult for a congenitally blind person to arrive at physical or astronomical knowledge, it is not impossible in principle. For the blind person could be equipped with photo-electric cells which react to incoming light rays from spectroscopes, telescopes or microscopes, etc. The photo-electric cells might then be connected through amplifiers with radio sets or other devices which through their emitted sounds, etc., would furnish discernible kinds of information in the auditory or tactual modalities. If this seems at first glance a bit fantastic, it should be remembered that our knowledge of stars that emit only either ultraviolet or else radio waves is just as 'indirect'. And so is our knowledge of the structure of atomic nuclei, of the spin of subatomic particles, etc., etc.
I contend, consequently, that a being with something like human intelligence (i.e., capacities for inference, theory construction, critical reasoning, etc.) might have a repertoire of sense modalities, and of immediate experience generally, that is utterly different from that of us earthlings; and that such a being (say, a Martian) might well arrive at the same concepts and theories as we do in the physical sciences. And if mind-body monism holds, the Martian could (in principle) also achieve complete knowledge ('by description') of the psychology of human beings -- including, of course, their sensations, perceptions, thoughts, emotions, moods, volitions, intentions, etc. -- all that on the basis of such behavioral and neurophysiological evidence as is accessible through his (the Martian's) sense modalities.
The piece of science fiction naturally leads to the question: If that is the nature of physical knowledge, can the physical sciences ever include the 'private', 'purely subjective' aspects of mental events? I shall try to answer yes, if the question is understood in one way, and no, if understood in another way. The answer customarily given in traditional philosophy is negative because it is felt that the qualities of immediate experience are 'homeless' in the physical account of the universe. Some thinkers (e.g., Bergson, Poincare, Eddington, Schlick, et al.) have in their various ways maintained a doctrine of the ineffability, inexpressibility or incommunicability of the 'content' of direct experience. Only the 'structure', so they say, is intersubjectively knowable and communicable. But on closer analysis this contention boils down to the obvious truth contained in the distinction between having (or living through, enjoying or suffering) an immediate experience (and thus being able to achieve 'knowledge by acquaintance' of experienced qualities) and knowing about it ('by description').
The -- at present -- utopian kind of physical knowledge can give an account of introspection, self-knowledge, avowals, etc. We may (somewhat speculatively) say that some part of the cerebral cortex 'scans' the processes in some other part of the brain. And since the scanning part would be the one connected to the motoric nerves of the speech organs, we can thus sketch -- at least by way of a 'promissory note' -- what the scientific account of 'private' mental states (and their avowals) would be like. It is this sort of speculation that makes (especially the Australian) materialists so confident that a physicalistic central state theory of mind is possible, and that it need not be incomplete. Indeed, in the frame of intersubjective science nothing need be 'left out' -- except the 'feel' of the 'raw-feels'.
This is why we must admit something is omitted in the intersubjective, scientific account, iiut what is omitted are not ineffable qualia or the like, for even in their introspective description we deal with their structural features. Whatever genuine knowledge we can attain is propositional. It reflects, for example, the similarities, dissimilarities (and degrees thereof) of the immediately experienced qualities. Propositional characterizations of these qualities would then isomorphically correspond to some structural features of cerebral processes, -- all this of course only if physicalism is assumed.
I think what is omitted or left out in the physicalistic (intersubjective) account of the world is not any event, process or feature. It is -- rather obviously -- the egocentric perspective which the intersubjective world view quite deliberately displaces and replaces. It is in the egocentric perspective (prominently stressed by Descartes, Berkeley, Hume and the positivists) that we label the qualia of immediate experience directly. (The 'successor' concept in the physicalist account is the scanning process mentioned above.) Now, the customary (and often ambiguous) uses of ordinary language to the contrary not withstanding, it is surely a 'category mistake' (of a special kind) to combine egocentric-subjective language with the intersubjective-physicalistic one. Most of the philosophical puzzles of the mind-body problem can be shown to originate from this sort of 'mixing' of terms belonging to two categorially different conceptual systems. The phenomenal (visual, tactual, kinesthetic, etc.) spatialities of the egocentric account are to be emphatically distinguished from the non-pictorial, unvisualizable concept of physical space. Similar distinctions have already been suggested above for the categorial differences between experienced qualities and the properties of physical objects.
In short, concepts which directly designate qualities of immediate experience and concepts whose meaning is largely independent of the specific ('ostensive') anchoring in one or another of the sense modalities, and which only by probabilistic indication refer to entities, events or processes in what we (somewhat misleadingly) call 'the physical world', are of an entirely different semantical type. Hence, if we wish to formulate a mind-brain identity thesis that involves more than the reduction of behavioral to neurophysiological concepts, a further step needs to be made. The identification of mentalistic (subjective, egocentric, private) phenomena with neurophysiological events or processes is then (as James Cornman put it) a ''cross-categorial'' one. In fact I should think this is the only cross-categorial identification required if we wish to relate the egocentric to the physicalistic accounts. All the other reductive identifications (as in physics, chemistry, and biology) are not really cross-categorial as long as we replace the naive realism (or direct realism) of cornmonsense with a clarified critical realism. But even from the point of view of cornmonsense, as Keith Gunderson has convincingly shown, we can clear up some of the perplexities of the mind-body puzzles by reflecting upon the epistemic asymmetries that obtain between one's knowledge of one's own mental states and one's knowledge of the external world as well as the mental states of others. Just as one cannot see one's own eyes (without the help of mirrors, etc.) so one cannot in the purely egocentric perspective perceive oneself entirely as a part of the 'physical world'. Just as one's eyes are not a part of one's visual field (Wittgenstein, Tractatus), so is one's brain (without the aid of an autocerebroscope) not part of the world perceived. Thus even within the "manifest image" (W. Sellars) of the world it is well-nigh impossible to escape; the egocentric orientation. But this is remedied in the inter-subjective scientific conception. Here the individual self becomes an organism among other organisms and all the rest of things and events that constitute the universe. Linguistically this 'great transformation' manifests itself by the disappearance of the egocentric particulars 'now', 'here', and 'I', along with all their cognate expressions. They are replaced by proper names, coordinates, definite descriptions, etc. The 'existentially poignant uniqueness' of the self of which we have heard so much in recent philosophy can be understood only within the frame of the egocentric perspective. Once the 'democratization' so characteristic of the inttersubjective frame is achieved, whatever uniqueness may remain is the usual empirical one of differentiating and individuating properties and relations. The directly experienced uniqueness is indeed inexpressible within the categorial frame of science.
(1) The arguments for the identity theory here suggested are primarily based on logical and epistemological considerations. While I think that the empirical evidence of psychophysiology makes it plausible that most forms of dualism and interactionism (along with the older forms of animism and vitalism) can be disregarded, the question of evolutionary emergence is still open. Equally unsettled is the question as to whether emergentism (if it could only be clearly formulated -- the essay by Meehl and Sellars is a notable attempt in that direction) is compatible with some form of monism. Personally I believe that the accumulating evidence points increasingly toward a (qualified) reductionism in biology and behavioral psychology.
(2) The identity theory that I favor does of course not require and could not accommodate nomological danglers in the intersubjective (scientific) theory of the world. But in the cross-categorial identification there remains the brute fact of the isomorphism of phenomenal with physical Gestalten. There does not seem any ready explanation of the difference in 'grain' between the phenomenal continuity (for example, of a smooth color-expanse, or the homogeneity of a musical tone) and the atomic structure of the 'corresponding' brain processes. It should be clear that the identity formulation (whose ascertainment depends upon empirical confirmation) holds only in extensional contexts. Like any other logically contingent identity it cannot be expected to hold salva veritate in all intensional contexts. Thus, to know that you are experiencing a certain mental event does not entail that you know with which brain process it is identical. (This is analogous to the case of the child who knows that the milk is warm without knowing anything about the mean velocities of the molecules of which the milk is composed.)
(3) The 'unconscious' mental processes as assumed in psychoanalytic theories can be viewed as quite legitimately postulated by means of explanatory theoretical concepts. These concepts are to be understood as analogues to familiar concepts designating conscious phenomena and/or as behaviorally indicated central processes whose neurophysiological nature is still largely unknown. Methodologically the situation here is somewhat similar to that of thermodynamics before the development of the kinetic theory of heat, or of chemistry before the introduction of the atomic theory. Philosophers who maintain that the idea of unconscious mental processes is inconsistent, merely reveal that they stick to an (unfruitful) terminological decision according to which 'mental' is defined as 'phenomenal' or 'conscious'.
(4) Does the identity theory suggest a panpsychistic metaphysics? No, if we conform to the rules of analogical inference, the differences between lifeless matter and the living organisms (and especially those equipped with central nervous systems) are too enormous for assuming similarities of their respective 'inner natures'. Nevertheless a pan-quality-ism (S. C. Pepper's term) is not unreasonable provided that the 'intrinsic qualities' of inorganic things or systems are conceived as incomparably more 'colorless' than the qualities of human experience. It should be evident without further discussion that any similarities of my identity theory with the metaphysical solutions of Spinoza's attribute theory or of Leibniz's monadology are only very superficial and largely coincidental.
(5) If a metaphysician is dissatisfied with the purely structural characterization of independently existing 'physical' entities, i.e., if he wishes for 'something more' than definite descriptions or Ramsey sentences, perhaps he can be consoled by being permitted to 'introject' the intuitive notion of existence. This notion of course has no place (makes no sense) in the intersubjective scientific conception of the world. But since Descartes was surely not talking outright nonsense when (in the famous "cogito ergo sum") he ascribed existence to himself, we may grant that this intuitive and subjective idea of existence is significant in the egocentric perspective. But, of course, it makes no difference that amounts to an intersubjectively testable difference in the scientific world perspective.
(6) The cross-categorial identity thesis should also be helpful for a better understanding of the causal account of perception. It enables us to relate in greater detail the egocentric (phenomenal or phenomenological) account of knowledge to the scientific one. In the intersubjective (scientific) account of perception we view (as we can and do already in everyday life) the knowing subject (person, organism) and the incoming stimuli as it were 'from the side'. In this 'lateral' perspective it is clear even to untutored commonsense that and why a blindfolded person cannot see environmental objects, and why, once the blindfold is removed, be can perceive them. This triviality can serve as an excellent antidote to the exclusively egocentric epistemologies of Berkeley and his positivist followers. Once the identity thesis is adopted the main (philosophical) puzzles of the causal theory of perception resolve themselves. The detailed psychophysiology of perception is of course still far from complete.
(7) Now to answer the perennial question: why not parallelism or epiphenomenalism instead of identity? As stated above, I don't think Occam's razor alone furnishes the answer. It is the mistaken conception of the physical (much more than that of the mental) that is largely responsible for such dualistic theories as parallelism or epiphenomenalism. I propose we mean by 'physical' the (structural) type of conception and/or whatever physical concepts (in this sense) designate or denote. And by 'mental' (but only for the purpose of the present essay) we mean what had better be called 'phenomenal'. To recapitulate: as was already seen quite clearly by Schlick and Russell, the physical (in the sense just defined) may well designate (or 'co-designate') those small parts of the world that are phenomenal as well. If so, one of the great 'mysteries' of modern philosophy has been (largely) dispelled. There is an identity of properties if we abandon picture thinking (naive and direct realism) about 'physical objects'. The identity is that of the structure of the phenomenally given with the structure of certain global aspects (Gestalten) of the processes in the cerebral cortex. The identity theory thus understood takes care of the traditional puzzles regarding the 'efficacy' of the mental (as in deliberation, attention, intention, volition, desires, pleasure, displeasure, etc.). Mental processes (being cross-categorially identical with brain processes, are of course among the most important causes of our behavior. And surely there is 'interaction' -- namely between the brain (as well as other parts of the nervous system) and the rest of the organism.
(8) It seems that analogies and homologies remain favorite devices not only in science but also in philosophical speculation and analysis. I found the application (made by N. Brody and P. Oppenheim) of Bohr's doctrine of complementarity to the mind-body problem interesting and suggestive. But on closer analysis, all I am able to accept is the categorial difference, and therefore (syntactical) non-combinability -- (incompatibility or non-compatibility seem to me inappropriate here) of the egocentric and the intersubjective conceptual frames. My differences from the outlook of the brilliant and sophisticate Australian materialism (of Smart, Armstrong, Medlin, Kekes et al.) should by now be evident. When radical physicalists argue for the completeness of their world-view, I object -- not on the usual (and to them acceptable) grounds, i.e., that science can never be known to be 'finished-in-principle'. Fully aware of the introduction of new entities throughout the history of science, they, of course, allow for such additions and modifications. (We all agree that science may well be, and probably is an 'endless quest'.) No, I am objecting to the physicalists' deliberate blindness in regard to something that -- admittedly -- does not amount to a surplus in the scientific-intersubjective frame. Hence I consider their arguments against the ψ-φ 'nomological danglers' as an ignoratio elenchi. It should be clear by now that the physicalists' assertion of the (potential) completeness of a physicalistic account of the world amounts to the truism (indeed the tautology) that there can be nothing within the intersubjective-physicalistic account of the world that is not intersubjective-physicalistic. An enormous amount of confused and fruitless disputes could be avoided once we recognize the game of the radical physicalists for what it is! These, admittedly keen and clearheaded philosophers, consistently (and alas, often unwittingly) apply the 'HYLAS TOUCH'! No wonder then, that whatever they deal with turns out to be 'physical'!
(9) Just a few words on the fashionable topics of 'intentionality', and the 'action' vs. 'movement' distinction. As in my previous publications I still think that (Brentano's notion of) intentionality is best explicated in terms of the semantical concept of designation. No matter as to whether mental imagery or imageless thoughts or words are on the subject side of the relation, the object (existent or non-existent) is the referent (symbolically) designated. Hence, despite first impressions, this part of the problem of sapience is not part of the genuine mind-body problem, but can be resolved within the context of the relation of the psychological (or physiological, or computerological, robotological) to the logical. The fallacies of psychologism are in any case to be avoided.
The colossal literature on intention (in the other sense -- in which it is connected with action) seems to me largely fruitless and exhibits glaringly the futility of the ordinary language approach in philosophy. Surely, there is a perfectly good meaning to causal explanations of intentional, purposive, goal directed behavior. Desires, ends-in-view, etc. furnish (like most explanation in terms of motivation) only the trivialities that even nursemaids and fishwives know very well, and that are still quite distant from genuine scientific explanation. To make a little clearer what was already known for centuries may be lexicographically useful, but it does not solve any philosophical problems.
(10) What sort of bearings my view has on the methodology of theory construction in psychology is clearly indicated in my essay 'Philosophical Embarrassments of Psychology' now republished in Duane P. Schultz (ed.) The Science of Psychology: Critical Reflections, New York: Appleton-Century-Crofts, 1970. My major previous publications on the mind-body problems are listed below.
Minnesota Center for Philosophy of Science