16 4.1 Mind and Body

4.1.1 Dualism

The view that material substance, — the physical body — and immaterial substance — the mind or soul — are two separate aspects of the self is referred to as dualism. Rene Descartes was by no means the first Western dualist (for example, Plato with his Theory of Forms is regarded by some philosophers as a dualist). However, Descartes’s dualism took a far-reaching and consequential hold on Western culture that has persisted for centuries. Descartes’s deeply personal reasoning and arguments for dualism provide a good starting point for looking at ourselves as physical bodies with mental lives.

Rene Descartes (1596-1650) is a prominent figure in modern philosophy; we encountered him in the Epistemology unit in connection the case he made for innate ideas. Besides leading him to realizations about what we know, Descartes’s first-person narrative of discovery, Meditations on First Philosophy (1641) details his journey from doubt to certainty on essential recognition of his dual existence as a mind and a body.

Note: Portions of the following material on Descartes are adapted from information in The Philosophy Pages by Garth Kemerling and is licensed under a Creative Commons Attribution-ShareAlike 3.0

The Second Meditation begins with a review of the First Meditation. Descartes is committed to suspension of judgment about anything he can doubt, and his doubts are extensive. He doubts input from his senses, and the material world may very well be a dream. An omnipotent God might render false any proposition he is inclined to believe. With everything seeming doubtable, does it follow that he can be certain of anything at all?

Yes! Descartes claimed that one thing remains true and undoubtable, even under the strict conditions he imposes: “I am, I exist” seems necessarily true whenever the thought occurs to him. This truth is not dependent on sensory information nor upon the reality of an external world,. He would have to exist even if he was being systematically deceived. Even an omnipotent God could not cause these two conditions to be true, at one and the same time:

  1. that he is deceived, and
  2. that he does not exist.

To be deceived, he must exist.

The meditation of yesterday has filled my mind with so many doubts, that it is no longer in my power to forget them. Nor do I see, meanwhile, any principle on which they can be resolved; and, just as if I had fallen all of a sudden into very deep water, I am so greatly disconcerted as to be unable either to plant my feet firmly on the bottom or sustain myself by swimming on the surface. I will, nevertheless, make an effort, and try anew the same path on which I had entered yesterday, that is, proceed by casting aside all that admits of the slightest doubt, not less than if I had discovered it to be absolutely false; and I will continue always in this track until I shall find something that is certain, or at least, if I can do nothing more, until I shall know with certainty that there is nothing certain. Archimedes, that he might transport the entire globe from the place it occupied to another, demanded only a point that was firm and immovable; so, also, I shall be entitled to entertain the highest expectations, if I am fortunate enough to discover only one thing that is certain and indubitable.

I suppose, accordingly, that all the things which I see are false (fictitious); I believe that none of those objects which my fallacious memory represents ever existed; I suppose that I possess no senses; I believe that body, figure, extension, motion, and place are merely fictions of my mind. What is there, then, that can be esteemed true? Perhaps this only, that there is absolutely nothing certain.

But how do I know that there is not something different altogether from the objects I have now enumerated, of which it is impossible to entertain the slightest doubt? Is there not a God, or some being, by whatever name I may designate him, who causes these thoughts, to arise in my mind? ….…

…But there is I know not what being, who is possessed at once of the highest power and the deepest cunning, who is constantly employing all his ingenuity in deceiving me. Doubtless, then, I exist, since I am deceived; and, let him deceive me as he may, he can never bring it about that I am nothing, so long as I shall be conscious that I am something. So that it must, in fine, be maintained, all things being maturely and carefully considered, that this proposition ‘I am, I exist’, is necessarily true each time it is expressed by me, or conceived in my mind.

Descartes’s reasoning here is best known in the Latin translation of its expression — cogito, ergo sum (“I think, therefore I am”) — from his work Discourse on Method (1637). The expression is not merely an inference from the activity of thinking to the existence of a thinker; it is intended as an intuition of one’s own reality, an expression of first-person experience, that cannot be doubted.

Descartes draws an initial consequence directly from his intuitive certainty of his “I think, therefore I am” argument. If I know that I am, he argued, then I must also know what I am. He believed that an understanding of his true nature must be contained implicitly in the content of his awareness.

He asks what this “I” actually is, the “I” who doubts, who may be deceived, and who thinks. Since he gained certainty of his existence while seriously doubting sensory information and the existence of a material world, he believed that the features of his human body could not have been crucial for understanding his “self.” This leaves only his thoughts. Thus Descartes concluded that “I am a thing that thinks” (res cogitans.) In Descartes’ terms, he is a substance whose essence is thought, in all its modes:

But what, then, am I? A thinking thing, it has been said. But what is a thinking thing? It is a thing that doubts, understands, conceives, affirms, denies, wills, refuses; that imagines also, and perceives. Assuredly it is not little, if all these properties belong to my nature.

Fast-forwarding to the Sixth Meditation, Descartes tried to prove that there is a material world and that bodies do really exist. His argument derived from his supposition that divinely-bestowed human faculties of cognition must be designed for some specific purpose. (The existence of God is an integral aspect of Descartes’s reasoning.) Since three of our faculties involve representation of physical things, his argument proceeds in three distinct stages.

  • First, since the understanding conceives of extended things through its comprehension of geometrical form, it must at least be possible for such things to exist.
  • Second, since the imagination is directed exclusively toward the ideas of bodies and of the ways in which they might be purposefully altered, it is probable that there really are such things.
  • Finally, since the faculty of sense perception is an entirely passive ability to receive ideas of physical objects produced in me by some external source outside my control, it is certain that such objects must truly exist.

Among the physical objects Descartes perceived are the organic bodies of animals, other human beings, and himself. Finally he is at the point at which he can consider his entire human nature. Is he a thinking thing, concerned with the organism seen in the mirror? And what is the true relation between between the mind and the body of any human being? For Descartes, the two are altogether distinct.

In the Sixth Meditation Descartes provides two arguments for his strict mind-body dualism, famously referred to as “Cartesian dualism.”:

  • First, since the mind and the body can each be conceived clearly and distinctly apart from each other, it follows that God could cause either to exist independently of the other, and this satisfies the traditional criteria for a metaphysical distinction.
  • Second, the essence of body as a geometrically defined region of space includes the possibility of its infinite divisibility, but the mind, despite the variety of its many faculties and operations, must be conceived as a single, unitary, indivisible being; since incompatible properties cannot inhere in any one substance, the mind and body are perfectly distinct.

In summary, the nonmaterial, thinking (soul) part of the self (res cogitans) is separate from the physical body (res extensa). The nonmaterial part is independent of the physical laws of nature and the body is subject to the physical laws of nature. The soul cannot be substantially affected by death; death is an alteration of the state of the physical body only. This is Cartesian dualism.

The effects of Cartesian dualism have been far-reaching and consequential. Cartesian dualism is deeply entwined with religious beliefs, for example that there is life for the soul after death of the body. Effects of this picture of mind and body have permeated other areas of our lives; for example, Cartesian dualism profoundly affected the practice of medicine for centuries, separating diseases of the body from diseases of the mind.

Among the significant problems with Descartes’s radical separation of mind and body is that it does not account adequately for the apparent interaction between the two. (He did propose that the pineal gland of the brain has a connection to the soul, but this does not go far toward explaining life of the soul after death of the body, for example.) Ordinary experience demonstrates that volitions of my mind cause physical movements in the body and that the physical states of the body produce effects on mental operations. However Descartes’s view maintains that the nonmaterial mind/soul is independent of the physical laws of nature while the body is subject to these physical laws.


Summarize Descartes’s personal journey from doubt to his belief in his existence as a thinking being with a physical body. 150-200 words.

Note: Submit your response to the appropriate Assignments folder.

4.1.2 Materialism

Instead of having two kinds of things, having just one kind of reality, physical reality, addresses the issue of causal interconnection between mental states and physical actions. This view, known as materialism, holds that everything real is physical and that all mental properties, states, and events can be wholly explained in terms of physical properties, states, and events. (The term physicalism, the view that everything can be wholly explained in terms of physical properties, states, and events, is often used interchangeably with “materialism” and will be here in this course; but it may have different connotations in some philosophical discourse.) While the brain as a physical entity figures in materialist theories, some materialist theories differ in how they explain our mental lives and consciousness in terms of physical reality.


The materialist theory known as functionalism analyzes mental states in terms of what they do, rather than of what they are. An example often used to explain the basic concept of functionalism is the mouse trap; the name of the object describes it’s function, what is does – it catches mice. It is not referred to as “a piece of wood with a loaded spring on it” or “a small wire cage with a door that closes abruptly.” As for mental states, take as an example the sensation of feeling energized, or even euphoric during or after vigorous exercise; this is a functional account, whereas physically it might be described as elevated secretion of endorphins, norepinephrine, dopamine, and/or serotonin.

The brief supplemental resources (bottom of page) provide further examples and review of functionalism.

Functionalism differs from identity theory, a form of materialism, in which mental states are actual biological/physical states of the brain, defined in terms of their reality status, what they are, rather than what they do or how they function. (It is interesting to note also that functionalism differs on this point also from Cartesian dualism, which defines what things are, not what they do.)

Eliminative Materialism

The materialist theory called eliminative materialism, holds that people’s common-sense understanding of the mind is false and that certain classes of mental states that most people believe in do not, in fact, exist. According to eliminative materialists, as progress continues in neuroscience, we will acquire a new biological vocabulary using brain states to describe mental phenomena like “memory” or “belief.”

The following description of eliminative materialism is adapted from information in a Wikipedia.org article found at Wikipedia: Eliminative Materialism [CC-BY-SA]

Eliminative materialism (also called eliminativism) is the claim that people’s common-sense understanding of the mind (or folk psychology) is false and that certain classes of mental states that most people believe in do not exist. It is a materialist position in the philosophy of mind.

  • Some supporters of eliminativism argue that no coherent neural basis will be found for many everyday psychological concepts such as belief or desire, since they are poorly defined. Rather, they argue that psychological concepts of behavior and experience should be judged by how well they reduce to the biological level.
  • Other versions entail the non-existence of conscious mental states such as pain and visual perceptions.

An eliminativist position about a class of entities is the view that the class of entities does not exist. For example:

  • materialism is eliminativist about the soul
  • modern chemists are eliminativist about phlogiston
  • modern physicists are eliminativist about the existence of luminiferous ether.

Eliminative materialism is the relatively new (1960s-1970s) idea that certain classes of mental entities that common sense takes for granted, such as beliefs, desires, and the subjective sensation of pain, do not exist. The most common versions are eliminativism about propositional attitudes, as expressed by Paul and Patricia Churchland.

While there is skepticism that future research will find a neural basis for various mental phenomena, philosophers like the Churchlands argue that eliminativism is necessary to open the minds of thinkers to new evidence and better explanations.

Patricia Churchland (1943 – ) and Paul Churchland (1942-) are committed to the view that neuroscientists, not philosophers, will solve the mind-body problem. Neuroscience is an emerging field, in its early days. While intriguing discoveries have been made about brain activity that accompanies certain behaviors, the present level of understanding is meager in comparison to what lies ahead. Indeed, philosophers are becoming aware that understanding the mind means understanding the brain. The brain exists, not the mind.

The Churchlands see what is referred to as “folk psychology” (also known as commonsense psychology) is a set of accumulated assumptions and hypotheses used to explain and predict other people’s behavior. Folk psychology is just another theory that will be proven wrong. It will be like other theories based on the best knowledge and assumptions available at the time: for example, the earth is flat, or the sun revolves around the earth. The Churchlands, citing examples such a research around the sensations that amputee patients experience in their missing limbs, believe that progress in the materialist endeavor of neuroscience may someday succeed in creating a map of the function and structures of the human brain that completely eradicates folk psychology. The brain exists, not the mind, and philosophers need to work with neuroscientists and psychologists to replace our current “folk psychology” with more accurate terminology and understanding of concepts like “the self” and “consciousness.” Updating the present-day vocabulary of “folk psychology” to the terminology of neuroscience (describing brain states) will be like progressing from Aristotelian to Newtonian physics.

A supplemental resource (bottom of page) provides more information on eliminative materialism.


Do you think that if you had deeper technical understanding of the brain states associated with the pleasures of life (whatever they may be) your experience would be diminished (less pleasurable)? Enhanced? Would have no effect at all? Explain your reasons. What about unpleasant emotions or experiences (fear, anger), would a deeper understanding of your brain states be a help or a hindrance?

Note: Post your response to the appropriate Discussion topic.

Materialism and Causal Connections

A significant problem encountered in Descartes’s radical mind and body dualism is that it cannot account for the apparent interaction between the two. Ordinary experience demonstrates that volitions of the mind (the will) cause physical movements in the body and that states of the body produce mental effects (including volitions of the mind.)

In seeing both mind and body as physical, materialism resolves this disconnect; the laws of cause and effect apply to the physical world. Indeed, causality can explain the interactions between our physical bodies and our mental lives. At the same time, causality invites a new question about ourselves. If every action is caused by a previous event, are our choices pre-determined? Are we acting freely when we make choices?

Supplemental Resources


Functionalism in 10 Minutes. This 10-minute video provides a clear presentation of functionalism.

Internet Encyclopedia of Philosophy (IEP) Functionalism. Read Section 2, The Core Idea.

Eliminative Materialism

Patricia Churchland on Eliminative Materialism Patricia Churchland explains her theory of eliminative materialism.


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