Mind-Body Problem

What color is a thought? How much does a thought weigh? How tall or short or how fat or skinny is a thought? Precisely where in space and time are thoughts located? What is the temperature of a thought? What is the speed of a thought?

Indeed these are very odd sorts of questions. The oddity itself is revealing: Thoughts do not seem to belong to the class of things that can submit to such questions or provide their answers. Thoughts do not seem to have size, shape, weight, color, velocity, mass, temperature, or location. Sometimes, of course, a thought can be described as "heavy" or "weighty," as in a philosophical discussion that considers such profound thoughts as "Is there a God?" and "Does my life have an objective meaning?" Thoughts can also be described as "dark," as in the statement, "The psychotic mind engages in dark thoughts such as murder and suicide." And people can speak of a "hot" idea, as in the slogan, "Wireless computers are now a hot idea." But these are all metaphorical uses of language. These statements do not literally mean that thoughts can have weight, color, or temperature. In short, the very nature of thought itself raises some serious questions.

Thought, or consciousness itself, does not seem to easily fit into the world of physical nature. In nature, people constantly encounter things with physical characteristics—trees, animals, automobiles, rocks, and other objects, all of which have physical properties such as weight, shape, and color. The human body, too, seems to belong to this world of nature, for it has size, weight, mass, and color. However, physical characteristics do not seem to be appropriate when discussing mental realities such as thoughts or consciousness in general. Does this mean that the mental world is somehow different from the physical? Does this mean that there are at least two separate realities or substances in the world: minds and bodies? Consequently, what will be the relevance of these questions to issues concerning death?


Dualism is the view that there are, indeed, at least two kinds of realities: the physical—characterized by measurable properties such as weight, location, size, and color; and the mental—characterized by nonphysical and immeasurable qualities such as immateriality. Dualism is a very old tradition, having many proponents. Some scholars claim that Plato (428–348 B.C.E.) was the first to make a sharp distinction between the mind and body. For Plato, the relationship between the mind and body is not an ideal one—in fact, the body can be seen as the "prisoner" of the mind or soul, which is the true person. In death, the mind and soul are separated. The body decomposes into its original elements, but the mind or soul cannot decompose because it is not a composed material substance. Therefore, the mind or soul cannot die. In Plato's works one sees the direct result of dualism with regard to the question of death: It provides hope for survival of the person after the death of the body.

However, other scholars argue the tradition of dualism did not begin with Plato. Perhaps the first philosopher to offer this position was Pythagoras (6th century B.C.E.). Pythagoras believed in the transmigration of the soul—the view that the soul is immortal and is bound up with the divine soul, to which it may return when "purified" after its separation from its temporary physical house (the body). Presumably there are any number of transmigrations of the same soul, as taught in the doctrine of reincarnation in religions like Hinduism.

Although Plato is not the "father" of dualism, certainly he provided a far more extended treatment and defense of the doctrine than anyone who came before him. The Platonic dualism had great influence on Christian thinking, though it could not be made perfectly consistent with scriptural views since Plato shared the Pythagorean belief in transmigration of the soul. The greatest of the early Medieval thinkers was Augustine (354–430) who held,

Man is not a body alone, nor a soul alone, but a being composed of both . . . the soul is not the whole man but the better part of man; the body is not ethe whole but the inferior part of man . . . and when both are joined they received the name of man. (Dods 1872, p. 24)

We can say that Christianity, for the most part, adopted a form of Platonic dualism as its official view, which went more or less unchallenged until Aquinas (1225–1274) who followed Aristotle's line of thinking on the mind-body relationship. Aristotle (384–322 B.C.E.) disagreed with Plato, his mentor and teacher, and provided a closer relationship between the mind and the body, claiming that the soul is the "form" of the body.

In modern philosophy it is René Descartes (1596–1650) who is most associated with dualism. Descartes's philosophy radically separates the mental and the physical, by claiming that they are, indeed, two very different kinds of substances. In his Meditations, he writes:

There is a great difference between the mind and the body, inasmuch as the body is by its very nature always divisible, while the mind is utterly indivisible. For when I consider the mind, or myself in so far as I am a thinking thing, I am unable to distinguish any parts within myself. . . . By contrast, there is no corporeal or extended thing that I cannot think of which in my thought I cannot easily divide into parts; and this very fact makes me understand that it is divisible. This one argument would be enough to show me that the mind is completely different from the body, even if I did not already know as much from other considerations (Cottingham 1966, p. 9)

But Cartesian dualism suffered from the beginning under the criticism of the "interaction problem." Namely, if mind and body are radically distinct substances, how is it that the mind and body can interact at all, as they obviously do?

Dualism has been under severe attack in the twentieth century, especially since Gilbert Ryle's book The Concept of Mind (1949). Some support for dualism, however, can be found in works such as Arthur Koestler's The Ghost in the Machine (1967); Karl Popper and Sir John Eccles's The Self and Its Brain (1977); and Zeno Vendler's Res Cogitans (1972) and The Matter of Minds (1984).


Those who deny that mind and body are two different and distinct realities, are called monists. Monism holds that there is only one ultimate reality, and that mind and body are essentially reducible to it. The oldest tradition within this view is known as materialism, which states that the ultimate reality is physical matter, and all that is or ever was arises out of and is ultimately reducible to matter. Perhaps the first real materialism is the view of atomism as proposed by Leucippus (c. fifth century B.C.E.) and Democritus (c. 460–360 B.C.E.). According to this view, all things are composed of indivisible particles of matter (atomoi). The human soul, too, is composed of "soul-atoms" which may be different from others in being smooth and spherical, but they are atoms nonetheless. Epicurus (342–270 B.C.E.) later adopted the Democritean materialism to argue that death is nothing to be feared since it is simply the dissolution of the soul into its original atoms. The Roman philosopher-poet Lucretius (c. 95–55 B.C.E.) also developed materialism as an attempt to rid human beings from religious fears by arguing against any nonphysical soul, and therefore proposing the mortality of all human beings.

The most important materialist in the modern period is the English philosopher Thomas Hobbes (1588–1679), who was greatly impressed by the progress during his day within science and mathematics. Galileo and Johannes Kepler, in particular, had shown the importance of using mathematics with careful observation of moving bodies in space. True knowledge, Hobbes felt, seeks to observe and understand true reality, which for him, is made up simply of "bodies in motion." For Hobbes, all reality and substance is corporeal or material. He firmly believed that someday science would be able to offer a full account of all reality based on a materialistic model, without recourse to a transcendent, incorporeal God. Nearly two centuries after Hobbes's death, Charles Darwin's Origin of Species (1859) and Thomas Henry Huxley's Man's Place in Nature (1863) provided scientific support for just such a materialistic explanation for the origins and development of life, without resort to any outside immaterial agency or deity.

In contemporary times, science has made some progress in showing that life itself may be understandable in terms of biological and biochemical terms. Much of the focus in the twenty-first century has centered on the question whether the mind can be completely reduced to materialistic and mechanistic functions. Many philosophers, beginning with the analytic thinkers, began to hold to a materialist or "physicalist" position. A variety of more or less materialistic views have emerged. One of the most popular theories to emerge since the 1950s is the "mind-brain identity theory," developed by Herbert Feigl, U. T. Place and J. J. C. Smart, which holds that "mental states are quite literally identical with brain states" (Borst 1970, p. 13). Other forms of materialism contend that mental states are reducible to "statements about behavior" and are therefore referred to as "behaviorism" (p. 15).

Perhaps the most famous philosophical behaviorist is Gilbert Ryle. His book, The Concept of Mind (1949), has had a major impact for many in discrediting dualism. Ryle refers to the concept of dualism as "Descartes' Myth" and as "the dogma of the Ghost in the Machine." The myth of dualism, he contends, is the result of a type of mistaken thinking which he calls a "category mistake." The example Ryle uses illustrates it best. Imagine someone on a campus visit of a university. He receives a full tour of the university, visiting the classroom buildings, the library, and the dormitories. At the end of the tour, the visitor then asks, "But where is the university?" He has mistakenly assumed that the university is some separate entity existing apart from all of its constituents. He has mentally placed "university" in the same category as "classroom buildings," "library," and "dormitories." But the university is not some separately existing entity alongside of the buildings that make it up; rather it stands for the entire collection. So, too, Ryle contends, the "mind" should not be thought of as some separate entity in the same category as "body" (or brain).

Partly because of Ryle's arguments, many philosophers have ceased to talk about "the mind" as a separate category. The focus since the 1970s has been on mental activity or consciousness in general. Perhaps the most audacious work comes in Daniel Dennett's Conciousness Explained (1991), which provides more attacks on dualism, but attempts to explain consciousness in terms of brain events has not avoided its critics either. Dennett himself agrees the task is difficult: "Scientists and philosophers may have achieved a consensus of sorts in favor of materialism, [but] getting rid of the old dualistic visions is harder than contemporary materialists have thought" (Dennett 1991, p. 37). Thinkers who have provided serious obstacles to any simple materialism include Jerry Fodor's A Theory of Content and Other Essays (1990), Roger Penrose's The Emperor's New Mind (1989), and John Searle's Intentionality: An Essay in the Philosophy of Mind (1983).

Relation to Death

The mind-body issue has crucial impact on questions concerning death. In the end, the materialist's position is that a person is identical with his or her body; or that the "mind" is identical with the brain and its functioning. When the body/brain dies, therefore, there is no continuation of the person; there is no hope for an afterlife. The dualist position does not identify the person with his or her body/brain. Therefore dualism leaves open the door for belief in an afterlife. For most, this is primarily a religious question that cannot be resolved by philosophy or science.

The mind-body issue has bearing on how one defines death. Does death occur only when the body expires? When exactly does this happen? The Harvard Brain Death criterion defines death as including a flat electroencephalogram (EEG). The materialist position would seem supportive of such a view. If death is the end of the person, and if the person is to be identified with something like brain functioning, then it would follow that one should define death as an event tied to something like a flat EEG.

But is there something like a mental death as well, which is totally separate from physical death? Consider such medical cases as Karen Ann Quinlan and Nancy Cruzan, where the brain is still functioning, but where the forebrain—the most human part of the brain—is destroyed. Both cases were famous U.S. euthanasia cases and each had their forebrains destroyed through illness. Cruzan's case (request for euthanasia by family) went to the U.S. Supreme Court (1989). Some scientists, along with the Quinlan and Cruzan families, argued that the patients in those cases (referring to the person as identified with some qualitative, human, mental life) were already dead; that is, Quinlan and Cruzan, as the persons the families knew before their accidents, were already gone. Keeping their bodies alive was, they argued, a grotesque injustice.

According to death researchers like R. S. Morison, the human being does not die as a unit. According to this view, life in any organism has no real sharp beginning and end points. Defining death is all the more difficult with a complex organism such as a human being. The dualist would seem supportive of this recognition that mental death (or the death of the person) may occur before and apart from physical death, because it does not identify the person with brain functioning. The mind-body debate, therefore, has relevance for a number of issues concerning death, such as religious concerns about an afterlife and moral issues such as euthanasia.

See also: African Religions ; Buddhism ; Chinese Beliefs ; Christian Death Rites, History of ; Immortality ; Islam ; Judaism ; Near-Death Experiences ; Philosophy, Western


Aristotle. Metaphysics, translated by W. D. Ross. In Richard McKeon ed., The Basic Works of Aristotle. New York: Random House, 1941.

Augustine. The City of God, translated by M. Dods. Edinburgh: T & T Clark, 1872

Borst, C. V. The Mind/Brain Identity Theory. New York: St. Martin's Press, 1970.

Dennett, Daniel C. Consciousness Explained. Boston: Little, Brown, 1991.

Descartes, René. Meditations on First Philosophy, revised, edited, and translated by John Cottingham. Cambridge: Cambridge University Press, 1966.

Fodor, Jerry. A Theory of Content and Other Essays. Cambridge, MA: MIT Press, 1990.

Guthrie, W. K. C. "Pythagoras and the Pythagoreans." In A History of Greek Philosophy. Cambridge: Cambridge University Press, 1971.

Hobbes, Thomas. Leviathan. New York: Dutton Press, 1950.

Morison, R. S. "Death: Process or Event?" In P. Steinfels and R. M. Veatch eds., Death Inside Out: The Hastings Center Report. New York: Harper and Row, 1974.

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Plato. Phaedo. In Edith Hamilton and Huntington Cairns eds., The Collected Dialogues of Plato. Princeton, NJ: Princeton University Press, 1961.

Pojman, Louis P. "What is Death? The Crisis of Criteria." In Life and Death: Grappling with the Moral Dilemmas of Our Time. Boston: Jones and Bartlett Publishers, 1992.

Ryle, Gilbert. The Concept of Mind. New York: Barnes and Noble, 1949.

Searle, John. Intentionality: An Essay in the Philosophy of Mind. Cambridge: Cambridge University Press, 1983.

Vendlar, Zeno. The Matter of Minds. Oxford: Clarendon Press, 1984.


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