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Materialism

I
Cartesian dualism and the Cogito

This is the doctrine that there are two real substances in the world — material substance out of which physical objects and bodies are made, and spiritual substance out of which souls are made. Descartes believes that both substances are real and exist independently of their being known (or experienced). He regards bodies as extended in real space and time. But mental experiences have no such extension. It is not possible to talk of the left hand side of a thought or the size of a sound. Thoughts, smells, emotions and sensations are examples of mental events that have no spatial extension, although they may have a temporal duration. In the Cartesian concept of the soul, the soul or mind is thought to be the “receptical” in which the mental events occur. It is a spiritual substance that is itself not extended in space and time; it cannot have extension in space because private mental experiences are not spatially extended. Descartes regarded the soul as the permanent, unchanging substratum of all experience. The soul is immaterial and strictly has no place in physical space and time. All changes that occur to a person are said to be accidental changes, and not essential ones. That is to say, they are like the changes that occur to a chair when it is painted a different colour; the colour of the chair has changed (with is the accidental property) but the chair itself (the essential substratum) has not.
Descartes in fact attempted to prove that the soul was a substance. This is the whole thrust of his argument as he works progressively through his Meditations. In the Cogito he maintains that he had direct acquaintance with the existence of his own consiousness, though he acknowledges that what that consciousness is, that he is, is as yet unclear. He seeks to clarify what direct experience tells him about the nature of his consciousness in his next propostion, sum res congitans, I am a thinking thing. In this proposition he explains that the essence of the soul is consciousness, though at this stage there would still be the possibility that such an essence could not exist apart from a body. It takes further arguments for him to convince himself that the soul is a distinct substance from the body — he argues that God must exist, that our experience tells us that mind and body are distinct, that God is not a deceiver and hence mind and body must be distinct substances.
from Descartes's Second Meditation

But what am I? ... Can I be sure that I posses any of those attributes that ... belong to the body? I pause to reflect, and I consider these attributes in my mind, and I conclude that none of them truly belongs to me. It would be tedious to pause to list them all. Let us move on to a consideration of the attributes of the soul, and see if any of these belongs to me. What about nutrition or walking...? But if it is true that I can have no body, then it is also true that I can neither walk nor eat. Another attribute is that of sensation. But one cannot have feelings without a body, and, furthermore, I have thought I perceived many things during sleep that on waking I realized that I had not experienced at all. What about thinking? And it is here that I find that thought is an attribute that belongs to me; it alone cannot be separated from me. I am, I exist, that is certain. But when is it certain? Just when I think; for it is possible that should I stop thinking completely, then I would likewise completely cease to exist. I am not going to believe in anything unless it is necessarily true: but to be precise, I am nothing more than a thing that thinks, that is, a mind or a soul or an understanding, or a reason, and these are terms that were formerly unknown to me. I am, nonetheless, a real thing and I really exist. But what thing? I have an answer: a thing that thinks.
This argument starts with the cogito. However, even the cogito is subject to intense critical attack. .
Hume: Enquiries

For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I can never catch myself at any time without a perception, and never can observe any thing by the perception. When my perceptions are removed for any time, as by sound sleep; so long am I insensible of myself and may truly be said not to exist. And were all my perceptions removed by death, and could I neither think, nor feel, nor see, nor love, nor hate, after the dissolution of my body, I should be entirely annihilated, nor do I conceive what is farther requisite to make me a perfect nonentity
Hume's attack lies at the heart of the empiricist rejection of the cogito. Hume maintains that when we self-reflect we are only conscious of individual perceptions, and never come across the soul as such. It is only ideas and (sense-) impressions that come fleetingly before us.

Hume: Treatise

... But setting aside some metaphysicians of this kind, I may venture to affirm of the rest of mankind, that they are nothing but a bundle or collection of different perceptions, which succeed each other with an inconceivable rapidity, and are in a perpetual flux and movement. Our eyes cannot turn in their sockets without varying our perceptions. Our thought is still more variable than out sight; and all our other senses and faculties contribute to this change; nor is there any single power of the soul, which remains unalterably the same, perhaps for one moment. The mind is a kind of theatre, where several perceptions successively make their appearance; pass, re-pass, glide away, and mingle in an infinite variety of postures and situations. There is properly no simplicity in it at one time, nor identity in different; whatever natural propension we may have to imagine the simplicity and identity. The comparison of the theatre must not mislead us. They are the successive perceptions only, that constitute the mind; nor have we the most distant notion of the place, where these scenes are represented, or of the materials, of which it is compos'd.
Therefore, we have no direct acquaintance with a spiritual substance that we could call the soul. The soul does not exist, or if we imagine that it does it is the immaterial container of its experiences. Strictly speaking, only the experiences exist.

II
The psycho-physical gap

The Cartesian view also extends to the nature of the soul's faculties — its abilities to perform certain functions. Between the soul and the body there is what is called the “psycho-physical gap”. The soul is not in space and time, the body is. Yet the soul instructs the body to move, and the body conveys perceptions to the soul. This causes the question: how does the one affect the other? It appears that the connection is a mystery.
Whilst the existence of the psycho-physical gap is a mystery and belies explanation, it is not in itself an absolute proof that the soul does not exist. There are plenty of things that we accept purely because they are descriptions of the reality we live in — for example, we accept that gravity acts between two objects with mass, though the origin of gravity belies explanation. Here is another mystery! In other words, the determined dualist can reply to the problem of the psycho-physical gap by saying, I don't know how mind and body interact, but they do!
According to the Cartesian concept of the soul, the soul has a special power to initial actions that would not otherwise occur according to the laws of nature. This is called freewill. The power of the will to choose between alternative actions is not subject to the causal laws of nature. The Cartesian concept pictures every action of an individual as being preceded by an act of volition. The volition might also be preceded by deliberation. In other words, a person usually first deliberates about what he is going to do, then takes a decision (act of volition), which is followed by an action. However, this model of volition, and its Cartesian assumption that it takes place in the soul, has been challenged in recent times, most notably by Gilbert Ryle.
The Cartesian model also leads to what Gilbert Ryle calls the “myth” of the “ghost in the machine”. This is the idea that the soul is somehow located inside the body, and directing the body from within it. It is the “ghost” that drives the body, just as a motorist drives his car. It is claimed by Ryle and others that this is an illusion. One possible cause of this illusion is the perspective of perception. All perceptions are referred to a center of perception, which is a point of consciousness just behind our eyes. This makes it seem that the soul is located just behind our eyes, or is associated with our brains.
Whilst Descartes himself may have subscribed to this view, and indeed argues specifically that there is a particular organ in the brain, the pineal gland, that acts as the gear stick for the soul (so to speak), a strict application of his philosophy should show us that there can be no point of contact between the soul and the body and no location of the soul. The soul is not in space and time, therefore, it cannot be located; and the unconscious assumption that it is located at the centre of our field of visual perception is an illusion, even within the Cartesian system.

III
Ryle and the Assault on Dualism

Ryle rejects the notion of a Cartesian spiritual substance, and accuses Descartes of making a category mistake. He calls dualism the “official doctrine”.
Gilbert Ryle: Descartes' Myth

The Official Doctrine

The official doctrine, which hails chiefly from Descartes ... every human being has both a body and a mind. ....

Human bodies are in space and are subject to mechanical laws .... but minds are not in space, nor are their operations subject to mechanical laws.

A person therefore lives through two collateral histories, one consisting of what happens in and to his body, the other consisting of what happens in and to his mind. The first is public, the second private.
In this extract he explains why dualism is absurd owing to a “category mistake”.
The Absurdity of the Official Doctrine

Such in outline is the official theory. I shall often speak of it, with deliberate abusiveness, as ‘the dogma of the Ghost in the Machine'. I hope to prove that it is entirely false, and false not in detail but in principle. It is not merely an assemblage of particular mistakes. It is one big mistake and a mistake of a special kind. It is, namely, a category-mistake. It represents the facts of mental life as if they belonged to one logical type or category (or range of types or categories), when they actually belong to another.
This is what the category mistake is
A foreigner visiting Oxford or Cambridge for the first time is shown a number of colleges, libraries, playing fields, museums, scientific departments and administrative offices. He then asks ‘But where is the University?' ... It then has to be explained to him that the University is not another collateral institution... the University is just the way in which all that he has already seen is organized. ... His mistake lay in his innocent assumption that it was correct to speak of Christ Church, the Bodleian Library, the Ashmolean Museum and the University, to speak, as if ‘the University' stood for an extra member of the class of which these other units are members. He was mistakenly allocating the University to the same category as that to which the other institutions belong.
He argues that it is a category mistake to treat the mind as if it were a substance.
Only physical objects have substance, and it is an error to ascribe substance to thoughts and ideas.
My destructive purpose is to show that a family of radical category-mistakes is the source of the double-life theory. The representation of a person as a ghost mysteriously ensconced in a machine derives from this argument.

The Origin of the Category Mistake

The differences between the physical and mental were thus represented [by Descartes] as differences inside the common framework of the categories of 'thing', 'stuff', 'attribute', 'state', 'process', 'change', 'cause' and 'effect'. Minds are things, but different sorts of things from bodies; mental processes are causes and effects, but different sorts of causes and effects from bodily movements. And so on.

... When two terms belong to the same category, it is proper to construct conjunctive propositions embodying them. Thus a purchaser may say that he bought a left-hand glove and a right-hand glove, but not that he bought a left-hand glove, a right-hand glove and a pair of gloves. 'She came home in a flood of tears and a sedan-chair' is a well-known joke based on the absurdity of conjoining terms of different types. .... I am not, for example, denying that there occur mental processes. Doing long division is a mental process and so is making a joke. But I am saying that the phrase 'there occur mental processes', does not mean the same sort of thing as 'there occur physical processes', and/ therefore, that it makes no sense to conjoin or disjoin the two.
Ryle also attacks the Cartesian concept of volition (freewill) arguing that there is no event at any stage of an action that corresponds to a act of volition. Acts of volition simply do not exist!
Gilbert Ryle: The Will

The Myth of Volitions

Volitions have been postulated as special acts, or operations, 'in the mind', by means of which a mind gets its ideas translated into facts. ... So I perform a volition which somehow puts my muscles into action. Only when a bodily movement has issued from such a volition can I merit praise or blame for what my hand or tongue has done.
... The first objection... No one ever says such things as that at 10 a.m. he was occupied in willing this or that, or that he performed five quick and easy volitions and two slow and difficult volitions between midday and lunch-time.

.... Thirdly, it would be improper to burke the point that the connexion between volition and movement is admitted to be a mystery. ... Transactions between minds and bodies involve links where no links can be.
For these reasons Ryle concludes that the concepts of spiritual substance and acts of the will (volition) are absurd.
Hence, mind as substance does not exist!

IV
Materialism — mind/brain identity theory

The mind/brain identity theory (often shortened to just “identity theory”) states simply that to be conscious is to have a brain process. In other words, consciousness is equated with a state of the brain.
A modern statement of this view is provided by J.J.C. Smart
J. J. C. Smart: Materialism

First of all let me try to explain what I mean by 'materialism'. I shall then go on to try to defend the doctrine. By ' materialism' I mean the theory that there is nothing in the world over and above those entities which are postulated by physics (or, of course, those entities which will be postulated by future and more adequate physical theories). Thus I do not hold materialism to be wedded to the billiard-ball physics of the nineteenth century. The less visualisable particles of modern physics count as matter. Note that energy counts as matter for my purposes: indeed in modern physics energy and matter are not sharply distinguishable. Nor do I hold that materialism implies determinism. If physics is indeterministic on the micro-level, so must be the materialist's theory. I regard materialism as compatible with a wide range of conceptions of the nature of matter and energy. .....

It will now become clear why I define materialism in the way I have done above. I am concerned to deny that in the world there are non-physical entities and non-physical laws. In particular I wish to deny the doctrine of psycho-physical dualism. (I also want to deny any theory of 'emergent properties', since irreducibly non-physical properties are just about as repugnant to me as irreducibly non-physical entities.) ....

But what about consciousness? Can we interpret the having of an after-image or of a painful sensation as something material, namely, a brain state or a brain process? We seem to be immediately aware of pains and after-images, and we seem to be immediately aware of them as something different from a neurophysicological state or process. For example, the after-image may be green speckled with red, whereas the neurophysiologist looking into our brains would be unlikely to see something green speckled with red. However, if we object to materialism in this way we are victims of a confusion which U.T. Place has called 'the phenomenological fallacy'. To say that an image or sense-datum is green is not to say that the conscious experience of having the image or sense-datum is green. It is to say that it is the sort of experience we have when in normal conditions we look at a green apple, for example. Apples and unripe bananas can be green, but not the experience of seeing them. An image or a sense-datum can be green in a derivative sense, but this need not cause any worry, because, on the view I am defending, images and sense-data are not constituents of the word, though the process of of having an image or sense-datum are actual processes in the world. The experience of having a green sense-datum is not itself green; it is a process occurring in grey matter. The world contains plumbers, but does not contain the average plumber; it also contains the having of a sense-datum, but does not contain the sense-datum.

It may be objected that, in admitting that apples and unripe bananas can be green, I have admitted colours as emergent properties, not reducible within a physicalist scheme of thought. For a reply to this objection I must, for lack of space, refer to my article 'Colours', Philosophy XXXVI (1961) pp. 128-42. Here colours are elucidated in terms of the discriminatory reactions of normal percipients, and the notion of a normal colour percipient is defined without recourse to the notion of colour. Colour classifications are elucidated as classifications in terms of the highly idiosynractic discrimatory reactions of a complex neurophysiological mechanism. It is no wonder that these classifications do not correspond to anything simple in physics. (There is no one-one correlation between colour and wave-length, since infinitely many different mixtures of wave-lengths correspond to the same colour, i.e. produce the same discrimatory reaction in a normal percipient.)

When we report that a lemon is yellow we are reacting to the lemon. But when we report that the lemon looks yellow we are reacting to our own internal state. When I say 'it looks to me that there is a yellow lemon' I am saying, roughly, that what is going on in me is like what is going on in me when there really is a yellow lemon in front of me, my eyes are open, the light is daylight, and so on. That is, our talk of immediate experience is derivative from our talk about the external world. Furthermore, since our talk of immediate experience is in terms of a typical stimulus situation ( and in the case of some words for aches and pains and the like it may, as we shall see, be in terms of some typical response situation) we can see that our talk of immediate experience is itself neutral between materialism and dualism. It reports our internal goings-on as like or unlike what internally goes on in typical situations, but the dualist would construe these goings-on as goings-on in an immaterial substance, whereas the materialist would construe these goings-on as taking place inside our skulls.
Most identity theorists do not state that consciousness is to be equated with the firing of particular neurons, but with the operation of the brain as a whole. That is, they reject an atomistic interpretation of the “consciousness = brain process” for a holistic one.
Mind/brain identity theorists conceive of awareness (for instance, visual awareness) as a kind of television screen in the brain. Gilbert Ryle argues in The Concept of Mind that thought arises through internalized speech, and that the larynx is very subtly moving and vibrating the skull when we are thinking. In other words, there are vibrations in the skull when we are thinking, and these vibrations constitute thought.
Identity theory is also often called “Centralism”, since it identifies states of the central nervous system (the brain and the spinal chord) with mental states. Identity theory denies the existence of a mind that is separate from the body, so it is also equivalent to materialism or physicalism. Physicalists argue that only the entities postulated by physics exist.
Biological naturalism is another term for physicalism. It is materialism with the view that mentalistic discourse should be reduced, explained or eliminated in favour of non-metalistic scientifically acceptable discourse.

V
Private and public language

The discussion of the relation between mind and body is often carried out by reference to two kinds of discourse. (a) There is the language of physical processes used in scientific observation, and regarded as being public and objective; (b) there is the language of mental process, or actions, intentions, motives, thoughts and meanings. Identity theorists argue that the second kind of language does not tell us anything genuine about the mind, and constitutes a mere “folk” psychology, which is superstitious and will eventually be replaced by an objective psychology.
That so-called objective psychology might entail some changes in the way in which what have formerly been called private mental states are ascribed. For instance, it is usually assumed that only the sufferer of a pain can truly know whether they are in pain or not. Sometimes we suspect that someone is faking it, like taking a day off work which isn't really needed. Identity theorists would presumably consider the possibility of an objective pain sensor. Let us imagine that advances in neurology are such that the precise centres of the brain that produce the sensations of pain have been identified. Then, a person visits the doctor for a sick note, saying he has a pain. The doctor scans his brain, finds no corresponding brain states, and refuses to issue the note. This raises some ethical issues!
Identity theory (centralism, physicalism, materialism) denies that there is a distinction between public and private objects. It denies that the contents of the mind are inalienably private whilst the objects of the real world are public. Their philosophy is supported by the claim that sense-data are before the mind not in the mind — a claim that was originally made by Russell. If sense-data are before the mind, then it is claimed they can constitute a separate world of publicly observable entities. In other words, both you and I can experience the same sense-datum. If the objects of direct acquaintance are sense-data, and these constitute the mind, and if the sense-data are public objects common to several observers, then they may also be discovered to be physical objects in the sense of being identical to states of the central nervous system, and hence finally, there is nothing over and above physical objects.
The reply must be to unpick this argument at some point, and essentially to reaffirm the distinction between what is before or in consciousness and hence is private only to one subjective consciousness, and what is independent of consciousness, and forms the public world. For instance, one can reaffirm that the basic properties of mental events are not the same as those of physical events. A sound does not have an extension is space, and so cannot be equated with an object (a state of the central nervous system) that does. The question — how wide is consciousness? — is absurd, indicating that consciousness itself does not have extension in space. Likewise, the absurd question — how long does consciousness last — indicates that consciousness does not have a duration in time either, although all experiences of consciousness last a certain time (such as listening to a phrase of music) and some have extension too (such as looking at a tree).
Likewise, it is possible to argue against the claim by Russell that sense-data can have an existence independent of the mind, and are not mental events, but neutral in some sense. Even if they are “before” rather than “in” the mind, it can still be claimed that they are private. How do I know that a sense datum that is before my mind (of which I am aware) is also a sense datum that is before yours (of which you are aware)? If the answer is that I don't know, then the sense-data are private regardless of whether one places them inside or just outside the mind — bearing in mind, also that the phrases “inside” and “outside” in any discussion of the mind must be metaphors, since the mind is not extended in space and time.

VI
Type a and type b language

We have already noted that he discussion of the relation between mind and body is often carried out by reference to two kinds of discourse. (a) There is the language of physical processes used in scientific observation, and regarded as being public and objective; (b) there is the language of mental process, or actions, intentions, motives, thoughts and meanings.
Language of physical processes, regarded as public and objective, has been called “type-a” language; language of mental processes, has been called “type-b” language.
Language of type-a is thought to be objective and capable of precise definition. It is also thought that, because it is based on extensions (classes and membership of classes), it is suitable for computer programming. In other words, a computer programme will eventually be described that is capable of expressing the relations of type-a language.
If language of type-b is admitted to be independent of language of type-a, then a theory of meaning for it will require notions that are incapable of definitions, concepts grasped by the mind, and properties and thoughts given through their intensions and not their extensions.
In the past, some identity theorists were committed to demonstrating that language of type-b could be reduced to language of type-a, and they set about trying to find ways in which aspects of type-b language could be translated into type-a language. They failed in their attempt, and intensional contexts have notoriously resisted this kind of effort.
In recent times a different approach has been adopted, that advanced by Davidson. This is a form of “anomalous monism”. In this theory the distinct nature of both types of language are accepted, and it is agreed that mental language is not a form of physical language. However, the mental language is not thought to refer to a special mental world. It is regarded as having either no coherent meaning (this is the position of Quine) or as referring to a physical world, but just in a different way. The mental and physical would be different descriptions of a world that is ultimately the same world, and also, ultimately physical.

VII
Epiphenomenalism

The Cartesian view of the mind, and its dualism of two substances, has currently been rejected by almost every philosopher of the Anglo-American tradition. Identity theory is one consequence of this rejection. However, some of these philosophers cannot quite accept identity theory — they acknowledge that whatever is before the mind remains private and describable only in first-person language; whilst the objective description of the world encountered in science is public and uses third-person language. Nonetheless, a number of these philosophers still regard the laws of nature as deterministic, and so, whilst consciousness cannot be equated by them with brain states, they regard consciousness as arising from brain states. This doctrine, that consciousness is a by-product of physical properties (and in the modern debate, of brain states) is called epiphenomenalism.
The term epi is Greek for “two”, and so epiphenomenalism asserts that there are two kinds of phenomena, the mental and the physical. However, in contrast to dualism, which would agree on this point, epiphenomenalism asserts that physical states cause the mental states, but the mental states do not cause physical states. The power of the mind to make things happen in the physical world is denied. It is a one way as opposed to a two way interaction between the mind and the brain. In epiphenomenalism, consciousness may be likened to a passenger in a car — the passenger goes where the car is driven, and similarly, consciousness is forced to go where the body takes it.
The debate between Naturalism (Materialism + Identity theory) and Epiphenomenalism (Materialism without Identity theory) is illustrated by the difference of opinion between John Searle and Particia Churchland.
John Searle (University of California, Berkeley) believes that there is a wide-spread assumption among philosophers that materialism is valid, but he is concerned with the problem of consciousness. For Searle, consciousness just annot be identified with brain-states, because it is a different kind of property. He puts this point in terms of different grammar. the language of science is said to be third person and objective; the language describing conscious states is said to be first person and subjective.
However, materialists, that is, identity theorists, regard first-person language as a form of superstition. They call it “folk” psychology and argue that it is false. In its extreme version this becomes the disappearance theory — the theory that we do not actually have beliefs, hopes and so forth, and it is an illusion to suppose that we do.
Patricia Churchland in her book Neurophilosophy is an out-and-out materialist and a proponent of the mind-brain identity theory. She argues that perceptions of sense-data are perceptions of brain-states. She does not equate conscious states with the firing of individual neurons, which is an atomistic theory, but with the organization of the brain as a whole, which is a holistic theory. She claims that the human organism is just a more complex version of animal organisms further down the evolutionary chain, and that in order to understand the human organism we should begin by understanding, for instance, how rats function. She does not believe that human beings have free-will, although she does admit there is a meaningful distinction between a voluntary and an involuntary action. She is also a positivist and believes that natural science will eventually arrive at a complete description of reality. She believes that the science of the future will have no need for the concepts of “folk” psychology, and that human behaviour will be entirely describable in terms of neurology.
Searle agrees with Churchland in stating that physical entities are the only things to exist, so he adopts a form of materialism. He denies that there is any kind of Cartesian spiritual substance. He disagrees with Churchland specifically on the point that consciousness is a brain state (and be identified with a brain state). He regards consciousness as a “higher” level property of certain physical objects, that is, as a higher level property of brains. Consciousness is a physical property, but it is not a physical entity. He uses the distinction between third person and first person observation to express this point, and claims that first person observation is not reducible to first person observation.
John Searle is an epiphenomenalist who opposes mind-brain identity theory, and who also argues that machines cannot have minds. He regards consciousness as a higher-level property of certain organisms (that is, of animals), and that only organic organisms with the right kind of history can have conscious states. In other words, he affirms that the correct criterion of judging when an object has a mind is a combination of behaviour and causal basis. A computer could not have a mind, because even if it behaved in every respect like a person, it would always lack the correct organic causal basis.
Nonetheless, Searle is a sort of materialist. He does not regard conscious states as existing in a substance separate from the body; but for him consciousness is a property of physical substances.

VIII
Behaviourism

Behaviourism is an attempt to study the mind purely from a scientific and mechanistic point-of-view. It has now given way to an alternative approach based on the mind/brain identity theory and the study of cybernetics. The idea behind cybernetics is to find computer programmes that duplicate the functions that are characteristic of the mind. Behaviourists tend to ignore the internal processes of the brain, and they explain psychology in terms of the mechanical responses of organisms to external stimuli. However, behaviourism and centralism (cybernetic theory) are clearly compatible, and the theories of the one can add to or build upon the theories of the other. Behaviourism stresses the external environmental factors in determining behaviour; centralism stresses the internal brain structure instead, which is thought to be genetically determined.
The claims of behaviourism are as follows:
(1) It is a science of the mind (a psychology) based on a study of that which can be objectively observed — based on the observation of the physical behaviour of animals. No behaviourist theory will ever allow into its vocabulary an idea that refers to a mental state as such. Cognition is not believed to play a fundamental role in the function of the organism.
(2) The central concept of behaviourism is that of a stimulus-response (S-R) bond. the organism is said to form a mechanical association between a stimulus and a response. The S- R bond is also called a reflex. (3) The fundamental pattern of learning is claimed to be by trial and error. This leads to conditioned reflexes.

IX
Replies to materialism

The modern debate has concentrated on attacking and rejecting Cartesian dualism. No other alternative picture of the mind and its relation to the body is serious considered as a contender. It is sufficient for Ryle, for instance, to debunk Descartes, for him to feel confident that the field is left open only to a form of materialism. The debate has subsequently narrowed to a consideration of whether the strict identity theory will be adhered to, or whether a form of epiphenomenalism will be preferred.
Even the debunking of Cartesian dualism has involved arguments and steps that have some doubtful claim to be convincing. Most obvious among these has been the rejection of the idea that sense-data are private.
The alternative to modern materialism must be supplied by some form of idealism, building on the work of Kant principally. Kant also sought to debunk Descartes, and the title of his greatest work The Critique of Pure Reason announces as its intention precisely this aim. It advertises the contents of the book as a thorough going attempt to expose the errors of logic of Descartes use of pure reason. Nonetheless, the idealist alternative to the mind/body problem has completely dropped out of view in the modern debate.