The Mind/Brain Identity Theory:
A Critical Appraisal

4. Taming the Phenomenal Qualities Tiger

4.3 Mind/Brain Identity as a Brute Fact

Book cover: Philosophy of Mind: A Contemporary Introduction by John Heil

I once thought that the only viable option for the identity theorist in demonstrating the veracity of his theory is the approach outlined in the previous section (§4.2). That is, by postulating a unified theoretical system from which novel predictions could be made and later confirmed. I am now more inclined to the view that there is another way open to him. This method consists in simply identifying certain mental states with certain brain states and claiming this identity to be a brute fact about the world requiring no further theoretical explanation. This makes some sense when we consider that the theoretical tools required for completely explaining human evolution and behaviour are already at our disposal. We already think that the theoretical concepts employed in neurophysiology and microbiology are sufficient for this purpose, so why make our job harder than we need to?

This move is not to be confused with the application of Occam's Razor; the principle of simplicity. The principle of simplicity is a methodological principle that applies to competing theories entailing the same empirical consequences. A postulation about what are brute facts, however, is a theoretical posit that leaves open the possibility of being disproved through further research. It is, in this sense, an empirical claim rather than a methodological manoeuvre. On this approach, then, the rival non-interactionist programmes, epiphenomenalism and psycho-physical parallelism, are to be defeated by historical and critical analysis. That is, by examining how they fared historically as scientific research programs as well as under the microscope of logical scrutiny.

As a lead in, let's start with logical analysis. Consider what I call the 'epistemological paradox' of epiphenomenalism. (This paradox holds for the earlier versions of property and substance phenomenalism as well as for the later interactionist epiphenomenalism. However, I shall state it here in the terms of the earlier property phenomenalism.) The paradox is this. The thesis of epiphenomenalism is that mental phenomena are non-physical properties of brain states that play no causal role in the production of bodily behaviour, including literary and speech acts. This thesis entails that the epiphenomenalist's literary and speech acts would have been and will be exactly the same, irrespective of whether or not there are any such non-physical, epiphenomenal properties; that is, irrespective of whether epiphenomenalism is true or not.

The paradox arises in that the epiphenomenalist is thereby barred from claiming to advance his thesis in literary or vocal form because he thinks he is aware of non-physical, epiphenomenal properties. This is so because, on his own thesis, the existence of such properties has not the slightest effect on what he says or writes. The thesis itself is not incoherent; it does not generate a logical paradox. However, it suffers from an epistemological paradox in that the epiphenomenalist is logically precluded, by his own thesis, from advancing reasons for his theory based on his awareness of such non-physical properties.[27]

The identity theorist is now in a position to charge the epiphenomenalist programme with complete heuristic sterility. On an epiphenomenalist account, no information whatsoever can be transmitted about the purported non-physical, epiphenomenal objects or properties; not even that they exist. In comparison, the identity theorist's programme is able to supply a very powerful positive heuristic. For example, the structure and properties of the mind can be tentatively modelled on the known structure and properties of the brain, while clues to the structure and properties of the brain can be gathered from introspectible properties of the mind.

The identity theorist may also claim that epiphenomenalism is an ad hoc retreat to a safe domain within the dualist programme (and so, on Lakatosian criteria, a point against epiphenomenalism). To substantiate this claim, though, the identity theorist needs to show that epiphenomenalism can be fruitfully construed as a move within a specifically dualist research programme, and so seen as a content reducing move within that programme. I'm unsure how successfully this can be made out. As well as the particular methodological problems involved in applying Lakatos' methodology of scientific research programmes[28] that the identity theorist must contend with, there remains the task of completing a detailed historical analysis of the programmes themselves. Only future research will tell how successful this claim will be.

However, it appears that whether we regard the formulation of epiphenomenalism as a move within a separate dualist programme or as a move within the identity theorists' own non-interactionist programme, the identity theorist possesses a crucial argument against the epiphenomenalist. And this is that regardless of whether, as a matter of historical fact, the construction of the epiphenomenalist theory happened after or before the construction of the identity theory, it is impossible for the epiphenomenalist programme to ever display an empirically progressive problemshift compared with the identity theorists' programme.[29]

Consider the first possibility. If the formulation of epiphenomenalism had happened after the formulation of the identity theory, then this move constituted a degenerating problemshift. It was degenerating because there is no prediction deducible from epiphenomenalism (in conjunction with background assumptions) that is not equally deducible from the identity theory (in conjunction with background assumptions). Epiphenomenalism is in principle unable to predict that if we perform such and such experimental procedures, we will discover (the effects of) non-physical properties or substances, for these, on the epiphenomenalists' own hypothesis, can have no discernible effect whatsoever on physical test setups. Of course, the epiphenomenalist can predict that if we perform such and such physical operations, such and such mental events will result, but this is equally deducible from the identity theory.

Alternatively, if the formulation of the identity theory had occurred after the formulation of epiphenomenalism, this would have constituted progress for the identity theorist's programme. This is because adherents to the epiphenomenalist programme could never justifiably assert anything about non-physical, epiphenomenal properties; not even that they exist. The assertion of any such statement, according to their own hypothesis, is equally consistent with there being no such properties. With no programme of research—no positive heuristic—epiphenomenalism is not only robbed of the potential of becoming empirically progressive, it is difficult to see how it could constitute a research programme at all. Compare this situation with the powerful positive heuristic of the identity theorists.

Book cover: Consciousness Explained by Daniel C. Dennett

What of psycho-physical parallelism? The only versions that the identity theorist need consider as a serious rival are those that offer an explanation for the correlation between mental events and some neurophysiological events.[30] For explanations that conscript the help of some supernatural being to establish or maintain the synchronicity, the identity theorist can point out the historical fact that this type of explanation is no longer a part of any tenable research programme. This is especially so since the research programme that sought to establish the existence of such a being (that is, theology) has been undergoing a degenerating problemshift since the Enlightenment.[31]

It is possible to maintain a form of psycho-physical parallelism while admitting that although we do not know the explanation for the correlation, nonetheless, there is one to be discovered. I am not aware of any researcher using this thesis as a basis for a research programme. If there is, I do not think that it should be rejected out of hand, for Newton's terrestrial and celestial mechanics programme held a similar status in this respect. The hard core of Newton's programme contained his Universal Law of Gravitation, a law for which Newton admitted he had no explanation. (For Newton, 'action at a distance' was an absurdity.) However, the identity theorist will rightly point out, Newton's programme otherwise enjoyed spectacular empirical success. Even so, following the singular lack of success from the strenuous search for an explanation for the law of gravitation, later Newtonians eventually abandoned the expectation for such an explanation.

The identity theorist would rightly point out that if such a psycho-physical research programme was established prior to the identity theorists' programme, then its lack of success in providing an independent confirmation of an explanation for the correlation signals its degenerating problemshift. If the programme was established after the identity theorists' programme, then it cannot supersede the identity theorists' programme until it furnishes us with an independently confirmed explanation, which it has not done to date.

So, with this second 'brute fact' method of attempting to substantiate his theory, the identity theorist is able to argue that his theory is rationally acceptable because his is a progressive research programme that has in fact not been superseded by any rival programme. As I have said, how far this argument can be pushed depends on the results of a detailed historical analysis of the rival programmes.

There is one outstanding objection to the identity theorist who takes this second line of argument. And that is that if it is simply a brute fact that certain mental states are strictly identical with certain brain states, as he maintains, then it is no longer obvious that what is being advanced is a materialist version of the theory. (Remember that we have already rejected 'logical gap' versions of the identity theory.) It now seems that there is an irreducible duality of types of physical states; those that are not identical to mental states and those that are identical to mental states.

What seems so implausible about all forms of dualism is that it is very odd to think that at some stage of our evolutionary development from amoeba to homo sapiens, and at some stage of our individual biological development from embryo to adulthood, there arises spontaneously, literally ex nihilo, irreducible non-physical substances and/or properties. This version of the identity theory seems to replace one form of fundamental dualism with another. It seems the identity theorist has managed to climb out of one deep hole only to have dug himself into another.

So, whatever approach the identity theorist takes to the problem of phenomenal qualities, he is burdened with unpalatable consequences. He may retain an uncompromising materialism, but at the cost of a promissory note regarding future theoretical research—research which may not turn out the way he envisages. Or he may attempt to win the rewards of rational acceptance here and now, but be burdened with the cost of completing a detailed historical analysis of the competing approaches to the mind-body problem. However, in so doing, he may seriously endanger his commitment to a thoroughgoing materialism.


  1. [27] I take it this is what Medlin was trying to say in his [1971: 110f].
  2. [28] An outstanding problem for Lakatos' methodology is the drawing up of detailed criteria for the identification of the boundaries of each research programme. So, in our case, the problem is whether we should identify two programmes; (property and substance) dualism and monism, and treat epiphenomenalism, parallelism, eliminative materialism, and so on, as moves within these two programmes. Alternatively, we could construe the two programmes as (non-physical–physical) interactionism and non-interactionism. Or we could even regard epiphenomenalism, parallelism, substance interactionism, the materialist identity theory, eliminative materialism, and so on, as separate programmes in their own right.
  3. [29] For Lakatos' criteria for evaluating research programmes in terms of problemshifts, see his [1978a: 31ff] and his [1978b: part 2, §8, 170–93].
  4. [30] The theory that every correlation is a chance correlation is rendered extremely improbable by the application of the probability calculus. The theory that the chain of physical causes and the chain of mental causes run in synchronism by chance alone had undergone a degenerative problemshift and is no longer a viable programme. This occurred primarily because not every mental event was found to have a mental cause.
  5. [31] A Lakatosian historical study of theology is another piece of historiographical research that is sorely needed.

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