Descartes writes that, “…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.” (Descartes, 59) From this he concludes that the mind and the body can exist independently. In this paper, I will present his argument, analyze the argument, and attempt to draw a conclusion based upon personal reasoning.

Descartes’ “Divisibility Argument” for mind/body Dualism is this:

1. The body is divisible.
2. The mind is indivisible.
3. Therefore, the body and the mind are not identical.

In support of Premise 1, he says, “…there is no corporeal…thing that I can think of which in my thought I cannot easily divide into parts…” (Descartes, 59). In other words, since the body is a physical entity, we can divide it into parts. In support of Premise 2, he says, “As for the faculties of willing, of understanding,…[etc.], these cannot be termed parts of the mind, since it is one and the same mind that wills [sic] and understands…” (Descartes, 59). In other words, although we might analyze the mind regarding specific functions, it is ultimately the mind as a whole which formulates thought as a single entity. Thus it is indivisible.

Now let us analyze the argument - does it hold water? It certainly seems to. To put the argument into a more logical format:

1. A is X. (entity A has quality X)

2. B is not X. (entity B does not have quality X)

3. Therefore A ? B. (entity A and entity B are not exactly the same)

Remember, we are not talking about specific minds or bodies, nor variations between entities of the same category – we are saying if two model entities differ in their properties, they are two different types of things. The challenge is not in the validity of the argument (it is valid), but the premises.

Let us begin with Premise 1 regarding the body. Is it true that you can always divide a body? The answer would appear to be yes. The reason is that the body, as Descartes noted, is a physical entity. Experience has shown us that people often sustain damage to their bodies. What about loss which renders the body incapacitated or dead? This (ie the condition of the body) would be irrelevant to the fact that it can be divided physically. What if we were to reach the limits of physical division (eg you divide a body until you are physically unable to divide it any longer)? In this case, we find that according to all known laws of nature, as long as we were able to develop the technology for it, it would be possible to divide it ever more minutely (take the example of a line, which according to geometry is infinitely divisible). Therefore it appears that all physical entities (which have “extension”, according to Descartes) are infinitely divisible, and thus so is the body, and it seems Premise 1 is True.

We turn now to Premise 2: the mind. Is it true that you can never divide a mind? To begin with, it should be pointed out that some people say that Premise 2 might beg the question. In other words, Descartes assumes something which itself is at the very core of the central question of the entire argument – is the mind distinct from the body, and if so, how? Therefore, for Descartes to assume that the body is indivisible is like “cheating” the argument. It did initially appear that way to me as well, but on second thought, I don’t think Descartes begs the question because the central question is NOT whether the mind is divisible or not – rather it is HOW are the mind and body different? And in reply Descartes “shows” how they are different – with his two assumptions. This is how ANY argument is constructed – with certain assumptions which may or may not be true. If I argued that “Mickey Mouse and Donald Duck are different.” and my assumptions were “Mickey Mouse is a mouse.” and “Donald Duck is not a mouse.”, these would be perfectly relevant to my argument. Of course, one could contest if indeed Mickey Mouse was a mouse or that Donald Duck is not a mouse, etc. I feel the argument not only is valid, but that the argument does not beg the question.

Now we are simply faced with the challenge of determining if we think Premise 2 is true or not. This question seems to have more complexity than the former because of ambiguity of definition – more specifically, what distinction shall we make of its essentials from its incidentals. In other words, what of the mind can we remove and still call the resultant entity a “mind”? From a neurological or psychological point of view, we do divide the mind into “parts”, but this, as Descartes himself points out when he mentions “parts” such as willing or understanding, is merely our effort to analyze specific functions or study the mechanics of nature and is not necessarily a “true” division.

To aid us, let us approach this issue from two distinct angles: the physical and the mental. Can the “mind” be divided physically? Descartes himself acknowledges a link between the brain and the mind, but continues to relegate it to a mere corporeal part, having an effect on the mind (Descartes, 61) just as your foot or your nerves, or indeed as the sight of a butterfly, may have an effect on your mind (the common link being things external to “the mind”). In other words, there is no absolute link, and the brain itself may be a cause of sensory or even cognitive error (Descartes, 61). Thus Descartes would say cut as much from the brain as you like, you would render the body incapable of perceptions and functions, but the mind is not what is being altered directly (in its essence).

From a non-material point of view, what if a person “lost” a part of his mind – what do we mean? We seem to make a distinction between essential and non-essential mental function. For example, we treat a person who suffers amnesia differently from one who is psychotic. One has lost the function of past memory but is still considered “sane” while the other is deemed out of touch with reality and mentally “ill”. Descartes himself mentions the example of madmen whose perceptions do not match reality (Descartes, 18) – yet we do not say that these people do not actually have minds, merely that they are dysfunctional. If dysfunction or loss does not render the mind literally “gone”, what actually does?

To take the case of non-material “parts” further, it seems that the mind is in essence not merely a collection of parts, and this is perhaps the point Descartes is trying to strike home. For example, there are stories of people who switch physical identities, keeping their “minds” or personalities, etc. while changing on the outside. In the story “Flowers for Algernon”, the main character undergoes changes in intelligence, which in some ways affect his personality. We do not think of a person who undergoes a lobotomy as a different person. Different in some ways, even in many ways, yes – we might say that someone “doesn’t seem himself” but we still recognize the person’s essence as something which transcends physical, mental, and even personality changes.

It seems then that for Descartes, if the “mind” is missing, then it is simply another way of saying the “essence” is missing. So the “mind” to Descartes is more a specific identity. In other words, you can splice a person from other people, and you would have a specific mass of parts collected into a new “body”, yet if you were to splice “pieces” of a mind, you would render the original “parts” devoid of essence, and furthermore not be able to form a new “essence”. It is like saying you take a part of someone’s existence – and this you cannot do. A person either exists or does not. So it seems that Premise 2 is also True. Therefore, the argument, which is valid, must also be True. However, a criticism might still be the muddling of the definition of “mind” with “existential identity” or at the very least being vague or ill-defined (perhaps he defines it more coherently elsewhere, but for a common-man understanding of this argument).

Despite the brilliance of Descartes’ argument, the question remains (perhaps due to the very criticism mentioned above): are the body and mind separate things? Modern science has shown ever-more evidence that the two are intertwined. Although the brain is vital to the body’s function, it seems that the body can be “brain dead” and yet kept in a vegetative state through medical facilitation. In the natural world, creatures with physical bodies exist without brains (eg plants). Therefore, the brain may be vital to a human being’s functioning, yet it does not seem essential for a physical creature (ie a body) to think (ie to have a mind).

So what of a mind existing without a body? We know that physical maneuvers (eg stimulating a certain part of the brain) incites corresponding mental reactions. There is definitely a physical basis for mental functions. So the actual question should be redefined as something more specific: are the mind and the brain independent? Again, a lot goes back to definitions – if we mean mental functions such as “cognition” etc. it is conceivable (as Descartes mentions) to have thinking beings without physical bodies (many people believe God thinks but is not a corporeal substance – however, it seems one cannot escape from the idea of a locus, even if immaterial). Perhaps Descartes was right in that the idea of mind is itself tied up in existential identity. Whatever mind/body connection there is (or isn’t), there is still an (as yet) undefined “gestalt” quality (the sum being larger than the dissected constituent parts). In conclusion, I do think that the mind and body are independent, yet with the humble consideration that this question, like most philosophical ones, might well defy absolute analysis.

Work Cited

Descartes, Rene, Meditations on First Philosophy, with Selections from the Objections and

Replies, translated by J. Cottingham, Cambridge: Cambridge University Press, 1986.

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