Descartes “argument of doubt”. Please do help explain

Question

Explain and critically evaluate (including at least one objection) Descartes' "argument from doubt" in support of dualism. Do you think that this argument shows that dualism is correct? Explain and discuss, supporting your answer with reasons.

Answer 1

One popular way of characterizing Descartes' best argument for dualism is as follows:

1. Descartes can rationally doubt that his body exists. (Descartes can doubt the existence of everything in the “external world.”)
2. Descartes cannot doubt that he exists.
3. Therefore, Descartes is not his body. (Descartes is none of the things in the corporeal or “external” world.)

We can understand this conclusion as being more or less tantamount to the assertion of dualism. Although it is worth noting that dualism is the thesis that the mind and body both exist and that they are separate entities, whereas this argument does not clearly assert the existence of extended things (e.g., Descartes' body).

The basic idea behind this argument is that one cannot simultaneously doubt and not doubt the existence of the very same thing. This is seemingly supposed to invoke the sort of intuitions that lie behind Leibniz's Law that no single object can possess two contradictory properties. For instance, something cannot be both completely red all over and blue all over. Similarly, so the argument goes for Descartes, one can doubt and not doubt the existence of a single entity.

Many people argue that the argument here is invalid (i.e., that the conclusion does not follow). To illustrate consider the situation Lois Lane is placed in when she does not know that Superman is Clark Kent. In the fiction of Superman, Lois Lane knows of Clark Kent as a somewhat dorky coworker and also knows of Superman as a heroic figure capable of self-propelled flight. However, she of course does not know that Clark Kent is Superman; these are two names of the same person. Now consider the following argument which is arguably analogous to Descartes':

1. Lois Lane doubts that Clark Kent can fly.
2. Lois Lanne does not doubt that Superman can fly
3. Therefore, Superman is not Clark Kent

The conclusion here is obviously false even though the premises are true (in the fiction of Superman). Hence, we must have an invalid argument on our hands. And thus, critics of Descartes' argument claim that the same is true of Descartes' argument.