Critically assess Descartes’ three arguments for his claim that mind and body are distinct. The concept of Mind-Body dualism is one that has its roots in early classical philosophy, with both Plato and Aristotle setting out strong arguments for this philosophy of the mind. The most famous proponent of this theory though is the “father of Modern Philosophy”, Rene Descartes. This belief fundamentally stems from the appearance of humans having both mental and physical properties, properties which seem to be radically different.
As a response to this Descartes proposed that these properties are contained within two radically different substances, res cogitans, or thinking substance, and res extensa, extended substance. This thinking substance is what makes up a mind and the extended substance a body. Within his Discourse on Method and the Meditations, Descartes outlines three arguments for this distinction between the mind and the body.
These arguments, varying in their strength, have been analysed fervently since Descartes published them, and much philosophy of the mind centred on Descartes theses until the beginning of the last century and debate still remains today. The first argument that Descartes sets out in his Meditations for mind body distinctness is what has become known as the doubting argument. This argument first appeared in the Discourse (Descartes, 1971, pp. 32) and he expanded upon it in the Meditations (Descartes, 1641, 2:6).
Though the argument changed structure slightly between the two texts it can be broadly seen as: P1- I can doubt that my body exists P2- I cannot doubt that my mind exists P3- Identical substances must have identical properties C- My mind and body are different substances. It should be noted before examining this argument further that the third premise is a general principle of Descartes’s employed in much philosophical discussion. This principle states that if something is true of X and not true of Y then they are distinct, or in other words if X has some property that Y does not they are entirely different things.
This principle is commonly referred to as Leibniz’s Law, or the Principle of the Indiscernibility of Identitcals. Descartes has previously shown in his meditations that all corporeal, physical things can be doubted and should not be assumed to exist. This is shown using his dream, deceiving god, and the evil demon arguments. Premise one then directly follows form the conclusions of this section in the meditations. He also previously concluded that the existence of the mind is indubitable, with his famous conclusion cogito ergo sum, or I think therefore I am (Descartes, 1641, 7:140).
Descartes’ second premise in this argument follows wholly from this assertion and cannot be questioned. The third premise, sometimes missing in analyses of the argument, is simply the principle of the indiscernibility of Identitcals. Though this premise is needed for the argument to flow logically its inclusion causes Descartes much difficulty. The strongest criticism of this argument is that this doubt is not a property of the substance; rather it is a property of the observer.
In other words, doubt about the existence of the thing does not come from what the substance is, but rather from ignorance on the part of Descartes. Many examples have been used to highlight the inherent weakness in this argument. Perhaps the earliest of these objections came from Antoine Arnauld in 1641 within his Fourth Objections. (http://www. earlymoderntexts. com/pdf/descobje. pdf, pp. 56-57) Here Arnauld uses the example of a right angled tri angle to show the flaw in Descartes reasoning.
He says that while a person may not doubt that an triangle is right angled, he can at the same time doubt that Pythagoras’s theorem holds. The person observing the triangle obviously does not have a clear and distinct perception of the triangle but how, Arnauld asks, is “But how is my perception of the nature of my mind any clearer than his perception of the nature of the triangle? He is just as certain that the triangle has one right angle as I am certain that I exist because I am thinking. ” This objection has come in other forms such as Blackburn’s Masked Man Fallacy (Think, pp. 9-30). Since this flaw in the argument was so obvious to even Descartes contemporaries, the question arises as to why he even chose to include it in his Meditations? Well it is clear from his own writings that Descartes was aware of this and explicitly states that he refuses to conclude that his mind is distinct because of his ignorance of his nature (Descartes, 1641, 7:27) Descartes second argument again tries to show that the mind and the body have different properties, and by utilising his general principle, must therefore be different substances.
This time though instead of using the inherently difficult property of whether a substance’s existence can be doubted, he examines each substance’s respective divisibility. His argument goes as follows: P1- My body is divisible P2- My mind is not divisible C- My mind and body are distinct This argument’s main merit, as opposed to the previous one, lies in the fact that the property it is concerned with, divisibility is one which is inherent in the object. As such the Principle of the Indiscernibility of Identicals can be applied here.
The inference then from the two premises is not one that can be attacked or need be justified. Likewise the first premise which states that a physical body can be divided is a biological fact and again one that cannot be questioned. Where the issues arise in relation to this argument is its second premise which states that a mind is a substance that cannot be divided, an assertion which is at best controversial. As one would expect Descartes justifies this belief through reason alone rather than by any scientific analysis.
He states that “”When I think about my mind—or, in other words, about myself insofar as I am just a thinking thing—I can’t distinguish any parts; I understand myself to be a single, unified thing. Although my whole mind seems united to my whole body, I know that cutting off a foot, arm, or other limb would not take anything away from my mind. ” (Descartes, 1971, pp. 138). This premise has two main issues related to it. Firstly Descartes here is committing the logical fallacy of begging the question.
This premise explicitly assumes that there is a difference between the mind and the body, which is meant to be what Descartes is proving (Hatfield, 2003, Chp. 8). Secondly this premise has also been entirely discredited thanks to modern work in neurophysiology we know that if a part of my material brain is removed something will also have been taken away from my mind. Similarly, when the group of nerve fibres connecting the two hemispheres of the human brain, or the corpus callosum is completely torn in an operation called a corpus callostomy, the mind appears to separate into two different conscious awarenesses.
The lay term for this phenomenon is split-brain. (Gazzaniga, 2005) For Descartes these modern developments would surely have undermined much of what he was trying to attempt in this divisibility argument. Descartes third argument is perhaps his most celebrated defence of dualism and it is his attempt to prove beyond doubt that the mind and the body are distinct. The argument runs as follows, with the references to God omitted for the purposes of clarity. P1-I can conceive that I, a thinking thing, exist without my extended body existing. P2-Anything that I can conceive is logically possible.
P3-If it is logically possible that X exist without Y, then X is not identical with Y. C- I, a thinking thing, am not identical with my extended body. Though this argument is widely discredited academics differ in their reasons for why exactly this argument is false. It appears that there are problems with almost all of the parts in this argument. The first premise has its roots in the first and second Meditations where Descartes, through his method of doubt and in particular the deceiving God argument, comes to conclude that a world consisting only of immaterial minds is conceivable.
Many ardent empiricists though would dispute the claim that a non-corporeal world such as this, which by definition is something entirely distinct from experience, is truly conceivable at all. The main problem with this premise though is that it assumes that Descartes comprehends his mind in a complete fashion. He claims that the thought process is a transparent one which he has a clear understanding of. This assertion is one that is by no means apparently the case. It is quite possible, and indeed common that our emotions and feelings, for instance, are no directly apparent.
Quite often we can have the feeling of fear without it being directly registered to ourselves. This is also true of the mental state of pain, which may not be directly at our disposal. This particular criticism was put forward largely by Gilbert Ryle, and largely led to the development of his philosophy of the mind, behaviourism (Ryle, 1949, p. 11). The second premise though is where most philosophers have found fault with Descartes’ argument. This assertion about logical possibility has been the subject of much debate up to the present time.
Arguments against have pointed out that statements of numerical identity (x=x, x=y) are necessarily true though they may be conceived as false. Arnauld’s example of the right angle triangle can be used here. True mathematical propositions are also necessarily true though they be conceived of as false as well. Goldbach’s Conjecture, which states that any even number greater than two must be the sum of two prime numbers, is an example of a mathematical truth that can be thought of as wrong. It is possible that I can conceive that someday a number that does not hold to this conjecture will be discovered.
Just because I can conceive of these two events does not mean they are logically possible. (Chalmers, 2002) Descartes in this argument fails to explain why his conception of the mind is different than these two other examples. It is quite obvious after analysing Descartes’ arguments that none of descartes’ arguments do not stand up to much intense scrutiny. Each of the three main arguments for dualism have their own distinct problems. It must be pointed out though that many of the stronger objections to dualism have arisen due to developments in the field of neurophysiology in this century and the last.
This information was not available to Descartes’ at the time, and while they may be valid criticisms of the arguments he put forward, we should not dismiss his work entirely. In contemporary philosophy there can be a tendency to ignore the long legacy of dualism and to simply dismiss it without thought, this is a trend that I see as Bibliography: Blackburn, S. , Think, Oxford University Press, Oxford, 1999 Chalmers, D. , “Does Conceivability entail Possibility? ”, Published in (T. Gendler & J. Hawthorne, eds) Conceivability and Possibility (Oxford University Press, 2002), pp. 145-200. ] Descartes, R. , Meditations on First Philosophy, 1641 Descartes, R. , Philosophical Writings, translated and edited by E. Anscombe and P. T. Geach, (Indeanapolis: Bobbs-Merrill, 1971) Descartes, R. , Arnauld, A. , http://www. earlymoderntexts. com/pdf/descobje. pdf, pp. 56-57, retrieved: 27/03/2013 Gazzaniga, M. S. , “Forty-five years of split-brain research and still going strong”, [Review], Nature Reviews Neuroscience, 6(8), 653-U651, 2005 Hatfield, G. , Descartes and his Meditations, Routledge, 2003 Ryle, G. , The Concept of Mind (1949); The University of Chicago Press edition, Chicago, 2002
