Descartes' Arguments for Mind-Body Dualism in His Sixth Meditation

In Descartes' sixth meditation he argues for the distinction between the mind and the body. He does this through two main arguments, which I shall paraphrase below. Of the four views of the mind body problem discussed in class, Cartesian Dualism is the view that I have found to be the most plausible. This is chiefly because of the lack, on the part of all three physicalist views, of sufficient explanation of and reason for subjective experiences.

I shall begin by giving Descartes' arguments for Dualism. The first argument is one of incompatible properties:

(Premise 1) The existence of all physical things, including my body, is dubitable.
(Premise 2) The existence of my mind is not dubitable.
(Premise 3) My mind, therefore, has different properties than my body.
(Conclusion) My mind is distinct from my body.

The second argument is one that utilizes Descartes' idea of things that are "clearly and distinctly" understood:

(Premise 1) It is conceivable that my mind could exist independently of my body.
(Premise 2) A conceivable proposition must also be possible.
(Premise 3) By P1 and P2, my mind can exist without my body.
(Conclusion) My mind is distinct from my body.

I shall begin with the first argument. In Descartes' earlier meditations (i.e. one and two), Descartes demonstrates the dubitability of all things corporeal and also the necessary existence, and therefore indubitablilty, of his own mind. This leads to the formation on the first and second premises in the first argument above. A brief synopsis of the reasoning behind the formation of the first two premises seems prudent. Descartes finds it easy to imagine that the entire physical world could be the result of a deception caused by something outside himself (i.e. God acting as a deceiver or "evil genius.") From this realization, he proceeds to assume the nonexistence of everything physical and to ask himself what is still known about the universe. He then realizes that the process of thinking, necessarily, requires existence of self, i.e. if one is thinking, then one must exist in order to be thinking. Also, if one is being deceived, one must still exist in order to be deceived. Thus, it becomes impossible to doubt one's own existence and one must be at least a thing that thinks.

The above two premises lead directly to the formation of the third premise, which is simply an observation that minds and bodies have at least one different property (i.e. dubitability of existence.) If two things have different properties, it is necessarily impossible for them to be the same thing and must, as a result, be distinct, which is the conclusion reached by Descartes in this first argument.

I believe the principle objection to this argument would be that dubitability is not a property of a thing itself, but rather one of the observer or contemplator of that thing. Yet, given Descartes' earlier claim that clear and distinct knowledge must come from God, who is not a deceiver, it seems that one's perception of a clear and distinct thing must in fact be a true reflection of that things intrinsic nature (i.e. if something were in fact indubitable, and clearly and distinctly perceived to be so, it must follow that that thing is intrinsically indubitable because that knowledge comes from a non-deceptive being.) Also, were the mind and body the same thing, as claimed by Identity Theorists, they must necessarily be perceived the same way because, being the same entity, it would be impossible for them to be perceived differently at the same time, because any observer would see only one entity. Consequently, if it is possible to perceive the mind and body as being respectively indubitable and dubitable at the same time, they must in fact be separate entities, as is argued by Descartes.

It seems counterintuitive that something such as a mind, which possesses complicated subjective states would be less dubitable (i.e. not at all) than physical things, which act according to precise and relatively simple laws. Thus, it may be observed that the mind is usually taken to be a less basic thing than a body, or anything physical. However, to Descartes, the exact opposite is true. It is the existence of the mind that must be clearly and distinctly perceived, not the existence of the body. Descartes, it must be noted, believes that things that are clearly and distinctly perceived must be, intrinsically, more basic than those that are not, making them possessed of different properties after all.

Perception thus becomes indistinguishable from reality because God is not a deceiver (a conclusion from his fourth meditation.) Descartes is very self-consistent in his argumentation and does appear to present a fairly sound argument for the distinction between mind and body via the fact that they have different intrinsic properties to them.

Descartes' second argument presents much more of a difficulty, chiefly because of the ambiguous nature of the words "conceivable" and "possible." The reasoning used to get from (P1) and (P2) to (P3) and consequently (C1) is quite good, but the problem arises when the truth-value of those premises is questioned.

The first premise (i.e. it is conceivable that my mind could exist independently of my body) is probably the most critical premise to the argument. It has already been shown, via the first argument above, that the mind is distinct from the body, but whether it does in fact have the ability to exist without being at least attached to a body is another matter. Empirical evidence seems to support the claim that minds must be attached to bodies in order to exist, despite the fact that they are distinct entities (e.g. minds have never been detected without their corresponding bodies.) However, the question is not whether empirical evidence supports the claim, but whether the premise is true, regardless of coincidental empirical observations.

This brings up the question of just what is meant by conceivability. I wish to make the assertion that something that is conceivable must contain no internal or definitional contradictions (e.g. it is inconceivable that there would exist a triangle with internal angles which total less than, or more than 180 degrees because the figure would no longer be a triangle.) Such a figure is not only inconceivable but also impossible. In fact any system which presents internal contradictions is inconceivable and consequently impossible. However, because we, as humans, are finite creatures, this definition of conceivability must be taken to mean "ideally conceivable," (i.e. conceivable by an omniscient being.) Consequently, it is likely that it is impossible for humans to truly know whether something such as the apparent conceivability of the mind's ability to exist independently of the body is, in fact, really and truly conceivable. It seems likely that Descartes is making a rather large assumption in his second argument, which is that because he 'clearly and distinctly' knows that his proposition is conceivable that that same proposition is in fact also 'ideally conceivable.' Thus, I believe that Descartes has taken his Dualism a step too far. While I do think that he is on the right track with Dualism as opposed to Physicalism, Descartes does also seem to be mistakenly putting himself in the position of an all-knowing being by claiming that he has the ability to know whether something is, in fact, truly conceivable or just apparently conceivable.

I wish to make another point regarding the mind and body's level of dubitability. Because of the fact that all physical things are not necessarily existent (i.e. they are dubitable) and the fact that the mind is distinct from the body, it does follow that the mind has the ability to exist independently of a body. If that were not the case, the existence of the body could not be dubitable because it (i.e. the body) would be a requirement for the existence of the mind, which is indubitable; however it has already been established that bodies are indeed dubitable. Consequently the mind must have an existence independent of attachment to a body.

While I agree with Descartes' conclusions, I think that his second argument must be found to be unsound because of the finite nature of human existence and consequently the inability of humans to correctly evaluate something as conceivable with certainty.

Dualism has a unique advantage over the other responses to the mind body problem (i.e. Functionalism, Behaviorism, and Identity Theory) because it does allow for subjective mental states. The main problem with each of those theories is that they never truly explain what it is like to experience something subjectively (e.g. physical occurrences of pain, thought, etc never describe the experience of pain, i.e. its essential qualities.) Of the three criticism of Dualism, Identity Theory seems to present the most problems for Dualism. While Identity Theory does not account for the subjective aspect of mental states, it does take into account the empirical observation of minds always being paired with bodies. However, the theory does fall far short of fully accounting for minds in terms of physical things. The mind allows for a subjective perception of things because, according to the Dualist view, it is a non-physical entity and therefore not subject to the objective physical laws which govern the behavior and workings of the physical universe. The mind is free to wander and perceive apparently at will, which is what may explain why mental experience and perception must be subjective. Were minds incapable of subjective perception, it would be impossible for two people to ever have a disagreement because the mind would be subject to the rigid paradigm of objective experience and perception. Yet obviously people do disagree and their mental perceptions do differ, and so it seems that the mind must be capable of subjective experience to prevent the consequence of universal agreement in perception, although I must admit that the actual mechanism of subjective experience remains unknown.

It is for the above reasons that I believe Descartes was on the right track by establishing the mind as a more basic entity than physical things. It does seem far likelier that it will be possible to explain physical objects in terms of mental properties (i.e. how they are perceived; e.g. dubitability) than it will be to explain mental properties in terms of physical ones. It is in this way that science and all other knowledge is obtained about the universe (i.e. through abduction and deduction.) Thus, we take raw data, which has no meaning in itself, and use mental properties to derive order from the data. Therefore I believe Descartes was correct in his perception of the mind being clearly and distinctly perceived as a necessarily existent object (as established in his first two meditations.)
In conclusion, it appears that there are more problems with the second argument than with the first, but because of the lack of explanation for subjective experience via purely physical objects by physicalists, it seems much more likely to me that Dualism is the proper approach to solving the mind body problem, regardless of the arguments presented by Descartes.