A Critique of the Mind-Brain Identity Theory – by Adebayo A. Ogungbure,Department of Philosophy, University of Ibadan, Nigeria


This paper attempts a critical examination of the mind-brain identity theory which holds that the mind or consciousness is nothing but a physico-chemical process in the brain. This theory is borne out of the quest by contemporary neurophysiologists and scientists to give an account of the operations of the human mind in pure physicalist terms, with particular reference to the complex workings of the human brain. If we are to take this view seriously, then we will be accepting the hypothesis that man is essentially a material being without any form of immaterial constituents whatsoever. However, it is doubtful whether this type of reductionist outlook of man provides an adequate understanding of the human person. This paper takes an exception to the identity theorists’ reductionist thesis by raising two objections against this theory. The first is on the difficulty of locating the neuronal correlate of consciousness or mental states which is attributed to brain activity. The second one stems from the implication the theory has for the doctrine of afterlife, and the belief in immortality popularly expressed by theistic persons. This paper concludes that the claim of the identity theorists is a case of mistaken identification of how the human brain works for a physicalist interpretation of consciousness and of the human person.


Over the years, philosophers have engaged themselves in the analysis of the nature of the human person and such preoccupation has led to the formulation of various theories and speculations about the nature of the human mind, the nature of the human body and the question of whether any forms of relationship can exist between the mind and body. This is now commonly referred to as the mind-body problem[1] in contemporary philosophy. It is also worthy of note that given the wide array of views on this subject matter, there are no consensual positions yet as regards the identity of the basic constitution of the human person. In this essay, however, we shall focus on the mind-brain identity theory[2] which basically identifies the human mind with the brain and ascribes the functions of the human mind to neural brain processes. It is a modern version of materialism referred to as central state materialism, which considers the human mind or consciousness to be a brain process. In the formal mode of speech this amounts to asserting that mental and physical expressions, although having irreducible meanings of their own and being mutually untranslatable, do refer to the same physical reality.[3] Consequent upon this notion, all human mental expressions of emotions like, sadness, pain, thirst, anger, love, hate and so on would be regarded as nothing less than the physicalist interpretation of stimuli and signals by the brain. This mind-brain problem which is still with us raises the question as to whether the mind is no more than the idle side-effect of our brain processes or whether the mind can, in some degree, influence behavior.[4] Following from this is the issue of how one can describe subjective mental events in the brain in accordance with the laws of physics as strongly advanced by the proponents of this theory.

Meanwhile, in discussing the mind-brain identity theory, one must pay attention to the scientific character of the theory. It is a well known fact that the proponents of the identity theory view themselves as champions of a scientific philosophy that strictly relies on scientific findings and methodology which is said to be free of a priori preconceptions and bold speculation. A good reason for the physicalist outlook of this theory lies in the identity theorist’s rejection of the dualist position which affirms that mental events are completely different from physical events because they are non-physical in all their aspects and consist in changes in the non-physical state of immaterial entity, the soul. In essence, the mind-brain identity theory denies what dualism affirms.[5] In fact, this theory holds that one can give a comprehensive account of man without recourse to any form of spirituality or ‘ghost stuff’. That is, as J.J.C. Smart claims, “for a full description of what is going on in a man you would have to mention not only the physical processes in his tissues, glands, nervous system, and so forth, but also his state of consciousness (which are his brain processes): his visual, auditory, and tactual sensations, his aches and pains.”[6] This statement by Smart, brings to the fore the scientific character of the identity theory. Our interest here is to critically examine the tenets of this science-inspired theory and the physicalist interpretation they gave to the human mental phenomena. Let us attempt a succinct conceptualization of the mind-brain identity theory.

An Overview of the Mind-Brain Identity Theory

This theory which came to prominence in the early 1950s and 60s and was advocated by philosophers such as U.T. Place, J.J.C. Smart, Herbert Feigl, and D.M. Armstrong, to mention a few. Although, there are slight variations in the position of these scholars, they generally hold the view that there is no existent immaterial substance called mind existing independent of matter. The mind-brain identity theory essentially holds that the mind is identical with and not ‘above’ or ‘over’ the human brain and that mental events are just brain activities. It also claims that there are no ghostly immaterial substances or events to constitute our minds. The arguments offered by proponents of this view are very instructive and compelling given the fact of recent developments in science which seeks to understand the human person from a purely scientific viewpoint.

In his famed article titled; “Sensations and Brain Processes”, J.J.C. Smart stresses this point by asserting that “a man is a vast arrangement of physical particles, but not, over and above this, sensations or state of consciousness.”[7] This statement by Smart reflects the denial of consciousness as something that has an independent existence outside the brain which is a physical entity.  A denial made possible by neurophysiology which is a major scientific influence on this theory, and has presented the world with radical views on how the human consciousness can be interpreted from a physiological basis and not in immaterial and mentalist terms as was the norm in classical philosophy. As Smart explicates further;

It seems to me that science is increasingly giving us a viewpoint whereby organisms are able to be seen as physico-chemical mechanisms…that is, for a full description of what is going on in a man you would have to mention not only physical processes in his tissues, glands, nervous system, and so forth, but also his states of consciousness: his auditory, and tactual sensations, his aches and pains.[8]

It is obvious from the above that the major thrust of this theory is to argue for the possibility of applying the method of scientific investigation in knowing the human mental state which is nothing but a physical expression of brain processes. For instance, electrical current can be applied to the brain of a person suffering from stroke or epilepsy to determine the pain mechanisms and tensions they are going through. Of course, such feelings of pain which is supposedly tangible, would be considered by the identity theorist as merely emanating from a physiological stimulating processes of the brain.

Similarly, U.T. Place in his work titled: “Is Consciousness a Brain Process?” suggests like other thorough going identity theorists that we can identify consciousness with a given pattern of brain activity, if we can explain the subject’s introspective observations by reference to the brain processes with which they are correlated. [9] But he believes that there is one obstacle that can hinder the understanding of consciousness in this way; this he referred to, like Smart, as Phenomenological fallacy.  To him, this phenomenological fallacy;

…is the mistake of supposing that when the subject describes his experience, when the subject describes his experience, when he describes how things look, sound, smell, taste or feel to him, he is describing the literal properties of objects and events on a peculiar sort of internal cinema or television screen, usually referred to in the modern psychological literature as the ‘phenomenal field.[10]

Thus, in order to avoid this mistake or obstacle, we must realize, as Place advocates, that we describe our conscious experience not with reference to any mythological phenomenal properties but to the actual state properties of the concrete physical objects, events and processes which give rise to the very conscious experience.

Although Place wrote copiously to defend his views, J.J.C. attempted a reformulation of his arguments by reasoning that to ascribe both immaterial and material qualities to man will be to commit Occam’s razor fallacy because there are no philosophical arguments which compels us to be dualists. He also granted the fact, unlike Place that there are certain undeniable facts about this vast mechanism called man. But he reduced such behaviours to dispositions and such dispositions are mentally derived, if this is the case, it follows that dispositions are brain processes. Smart unwittingly stressed the thesis of the mind-brain identity theory as follows; in his words:

Let me first try to state more accurately the thesis that… in so far as a sensation statement is a report of something that something is in fact a brain processes. Sensations are nothing over and above brain processes.[11]

It is obvious from the above that the mind-brain identity theorists hold a materialist view of man that everything including one’s own consciousness, thoughts, and sensations are purely material or physical. They take an uncompromising attitude towards the belief in minds conceived as non-physical in nature. They rejected the any interpretation of the mind as something phenomenal, subjective and private as conceived by the dualists. For them, mental phenomena do not enjoy any existence ‘over’ and ‘above’ the physical phenomena; in short, they are to be considered as physical phenomena. Extreme materialists like J.J.C. Smart assert that “conscious experience must be processes involving millions of neurons and are therefore explainable as ‘brain states’ and not ‘spirit’ or soul states.”[12] From this premise, it becomes obvious that the advocates of this theory are monists of the materialistic bent because they argue that only material substance and their states exist.

According to the major proponents[13] of this view, everything human beings think, feel, sense, will or desires are explicable in the term of physics because human sensations can only make sense when it is interpreted as the process of exchange of information between the nerves, central nervous system and the brain which are all material or physical in nature. The emphasis on the physical existence is referred to as physicalism in contemporary philosophy of mind. The term physicalism as described by Thomas Nagel is the idea that a person, with all his psychological attributes is nothing over and above his body, with all its physical attributes.[14] This claim is consistent with the physicalist claims that:

Human beings are fully material entities whose workings and properties may be completely explicated by the concepts and theories drawn from an ideally complete physics. There is no room for immaterial or supernatural interventions in the physical causal chains which run through a person’s central nervous system, reaching from inputs in the form of physical stimuli through behavioural outputs.[15]

It follows from this description that human beings are considered by the physicalist as parts of the natural, non-spiritual, physical world, not in any way related to the supernatural ghost or spirit mysteriously associated with the body. Thus for the physicalist, it is wrong to conceive of a mind as a separate substance from the body, because whatever the mind is, it cannot be immaterial. If this is the case, then some account that locates it entirely within the natural world must be possible. This physicalist trend running through the ideas of the philosophers of this persuasion shall now be subjected to a critical evaluation.

A Critical Evaluation of the Mind-Brain Identity Theory

Let us begin our critique of this theory with the first objection raised against it; which is that the mind-identity theory creates a difficulty of locating the points of correlation of consciousness within the brain. If consciousness which includes a person’s mental functions and self awareness are said to be causally related to or dependent on activities in the brain, then it would seem that consciousness share the same characteristics with neurons, brain cells and tissues. The claim that consciousness can be reduced to physiological processes is untenable since when we are talking about consciousness, there are the internalist and externalist aspects. The internalist aspects are those which are subjective to a person, like holding of beliefs, opinions, rational thinking, and other mental actions. The externalist aspect, on the other hand, has to do with the external world, like an awareness of one’s surroundings, being awake and experiencing the natural world. The identity theorists seem to interpret consciousness only from the internalist perspective without paying attention to the externalist aspects of consciousness.

Again, even if the brain is believed to be responsible for our conscious states, the question on whether the neuronal correlate of consciousness is physical would still persist. Is human consciousness just as physical as the tissues that make up the brain or are they immaterial qualitative states that subsist inside the “brain stuff?”[16] Can we speak of the mind or consciousness as brain processes in this way without falling into some kind of categorical confusion? It would be quite impossible as physicalism cannot grant that consciousness which it tried to reduce to mental state has certain incorporeal and distinctive features. Consequently, speaking of locating neuronal correlate of conscious states in the brain as the physicalist conceives it, is indeed a difficult task.  Although modern day physicalist believe that every conscious precept, how the brain represents stimuli from the senses is associated with a specific coalition of neurons acting in a specific way. That is, there is a sort of unique neuronal correlate of consciousness. Thus, the questions we can raise here are: how the brain processes does translate to consciousness? How are this physical process connected with the facts of consciousness? The chasm between the two classes of phenomena would still remain intellectually impassable. In short, the passage from the physics of the brain to the corresponding facts of consciousness is unthinkable.[17]

Contrary to the claims of the identity theorists, human consciousness cannot be reduced to mere physical processes in the brain because consciousness is that aspect of man which involves human experience and awareness of such experience. It is not a material process in the brain because it is not physical, measurable or scientifically quantified. If the mind-brain identity theory were to be true, then how come we do not know when the brain interprets our mental activities just as the brain interprets other reflexes like electric shock, or burns? Another issue that may posit a problem for the advocates of this theory is the fact that it would be difficult to interpret how a Being can be conscious of her consciousness in physicalist terms. In short, the doctrine of the passage from the physics of the brain to corresponding facts of consciousness in explaining the idea of the human person is a case of mistaken identification.

The second objection to the mind-brain identity theory stems from the fact that it has a serious implication for the doctrine of afterlife and immortality held by many religious people around the world.  The mind which the materialists identified with the brain is often regarded as the soul by theistic persons. For instance, Descartes uses the word “mind” to refer to the soul. He used the mind interchangeably with the soul and the soul for him, is capable of immortality. He believes that with this kind of consideration, it is possible to show that the destruction of the mind does not follow from the corruption of the body, and thus to afford men the hope of a life after death. This Cartesian presumption is similar to what we find in many theistic metaphysics nowadays. The Traditional Yoruba African Religion provides us with a good insight here. The Yoruba believe that there is a state of existence, attainable by human beings, beyond the limits of our present mortal life spans. That there can be some kind of continuation in existence after death is attested to by the actions and practices of living people such as veneration of the ancestors, ancestral festivals, and concept of the ‘living-dead’, belief in spiritual superintendents of family affairs and punishment of moral offenders.[18] In this case, the soul or spirit is believed to have the capacity to transcend death, and enjoy eternal life or eternal doom after death, depending on whether that soul was good or evil during its sojourn on earth. In fact, it is further believed within this system that one’s fore-bears can become ancestors and serve as mediators the supernatural world and the physical world, providing access to spiritual guidance and power.  Thus, within this kind of belief system and such religio-cultural framework, the mind-brain identity theory cannot hold because it reduces man to a purely material being who cannot transcend death. This is a shortcoming of their scientific vision. It suffices to note that scientifically speaking, human beings may not know what happens after death, but many are adamant that there is life after death.[19]


So far, we have been able to examine the main thesis of the mind-brain identity theory which postulates and defends the sameness of reference to mental and physical properties in understanding the human person, in terms of mind and the brain. Some objections to this theory have also been raised especially as it concerns its physicalist conception of man. But as we conclude, it is pertinent to state that although the theory entails a kind of extreme reductionism, it also has some merits because it is true that the mind or consciousness needs the brain in order to function properly. However, this close connection between the mind and the brain neither guarantee the assumption that the mind and the brain are the same thing nor consciousness is a brain process. It is quite difficult to grant the view the identity theorists are putting forward, because consciousness is not a material entity that can be qualified in the same physicalist way as other bodily experiences. It is the considered opinion of this paper that human consciousness is not qualitatively identical with brain processes.

Notes and References

[1] This notion is explicated by Peter Lloyd; he opines that the mind-body problem has remained essentially unchanged since Descartes put it forward in 1641. The problem is: what is the nature of the conscious mind, and how does it relate to the body? See. Peter B. Lloyd, “Is the Mind Physical?” in Philosophy Now, No.6, 1993, pp.1.

[2] The mind-brain identity theory is otherwise referred to as central state materialism or identity theory or modern physicalism.

[3] Fanny L. Epstein, “The Metaphysics of Mind-Body Identity Theories” in Nicholas Rescher (ed.) American Philosophical Quarterly, Vol. 10, No.3, 1973, p. 111.

[4] This mind-brain problem which is a fall out of the identity theory is stated clearly by John Beloff when he writes that however contentious, the philosophical problem of this theory as distinct from the physiological problem can be stated quite simply as follows: What, essentially is the relationship between events in the brain and those private, subjective, introspectible experiences that together constitute our inner mental life? This concern raised by Beloff is consistent with our first reason for rejecting the thesis of the identity theory which shall be attended to later in this paper. See. John Beloff, “The Mind-Brain Problem” in Journal of Scientific Exploration, Vol. 8, No. 4, 1994, p. 509.

[5] The disagreement between the dualism and identity theory consists in the acceptability of whether human beings possess separate mental or spiritual aspects that is independent of the body.

[6] Here, Smart stated the thesis of identity theory when he writes that: it is not the thesis that, for example, ‘after image’ or ‘ache’ means the same as ‘brain process of sort X’ (where ‘X’ is replaced by a description of a certain sort of brain process). It is that in so far as ‘after-image’ or ‘ache’ is a report of a process, it is a report of a process that happens to be a brain process. See J.J.C. Smart’s influential work; “Sensations and brain Processes”, Philosophical Review, LXVII, 1959, pp.141-56.

[7] J.J.C. Smart, “Sensations and Brain Processes,” in V.C. Chappell (ed.) Philosophy of Mind (Englewood Cliffs, 1962), pp.160-172. Also, this same article is published in David J. Chalmers, (ed.) Philosophy of Mind: Contemporary Readings (New York: Oxford University Press, 2002) pp.60-68.

[8] Ibid.

[9] Ullin T. Place, “Is Consciousness a Brain Process?” in British Journal of Psychology, 47:1, Feb 1956, p. 44.

[10] Ibid., p.49.

[11] J.J. C. Smart, Op.Cit., 55.

[12] J.J.C. Smart, “Materialism” in Feigl Herbert (ed.) New Readings in Philosophical Analysis, (New York: Appleton-C, Croth Corp., 1972) p. 378.

[13] The philosophers that are often recognized as the major proponents of this theory were deeply influenced by the writings of the logical positivist like Moritz Schlick, Rudolf Carnap, Carl Hempel, and even Bertrand Russell. They are regarded as Tough-minded scientists who tend to refute the claims of those whose mission was to relegate the mind-body problem to the limbo of speculative metaphysics. The works in this category of includes the works of the following philosophers: (i) Herbert Feigl, “The ‘mental’ and the ‘physical’,” in Herbert Feigl, Grover Maxwell, and Michael Scriven (eds.), Minnesota Studies in the Philosophy of Science, vol. II (Minneapolis, 1958), pp. 370-497. (ii) J.J.C. Smart, “Sensations and Brain Processes,” in V.C. Chappell (ed.) Philosophy of Mind (Englewood Cliffs, 1962), pp.160-172. (iii) Ullin.T. Place, “Is Consciousness a Brain Process?, “ in V.C. Chappell (ed.)Philosophy of Mind (Englewood Cliffs, 1962), pp.101-109. (iv) Hilary Putnam, “Minds and Machines,” in Sidney Hook (ed.), Dimensions of Mind (New York and London, 1960) pp. 138-164.

[14] See. Thomas Nagel, “Physicalism,” being the text of a Paper read to the Pacific Division American Philosophical Association in Seattle, 5 September, 1964.

[15] K.T. Maslin, An Introduction to the Philosophy of Mind (Cambridge: Polity Press, 2001), p. 73.

[16] The expressions “Brian Stuff” and “Ghost Stuff” are oft quoted terminologies of J.J.C. Smart.

[17] John Tyndall, “The Limitations of Scientific Materialism” in Paul Edwards & Arthur Pap (eds.) A Modern Introduction to Philosophy (New York: Collier-Macmillan Publishers, 1973) p. 217.

[18] Ade P. Dopamu, “Change and Continuity: The Yoruba Belief in Life After Death” The Text of a paper prepared for “Continuity and Change: Perspectives on Science and Religion”, June 3-7, 2006, in Philadelphia, PA, USA, a program of the Metanexus Institute (www.metanexus.net), p. 1.

[19] Ibid.

Contact the author at: Philosopher.bayo@yahoo.com or +2348032347935

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