Descartes' argument goes something like this:
#1) I can doubt that my body exists.
#2) I cannot doubt that I exist as a thinking thing.
#3) I, a thinking thing, am not identical with my body.
Essentially--if I understand this correctly--the logic he is using is that if two things are identical, or 'the same thing', then it should be impossible to imagine a possible world where one exists and the other does not exist, since that would be a logical contradiction (Law of Non-Contradiction). For example, I can imagine a world where bullfrogs exist, but in that same world, I cannot
imagine that amphibians do not exist. Therefore, they must be the same thing. And that is correct because bullfrogs are amphibians. If they were different, then it should have been possible to imagine one existing and the other not existing. In order to get this second point by, let us use another reverse analogy. I can imagine a world where Orthonorm exists, and in that same world, I can
imagine whiskey not
existing. Therefore, we can conclude that Orthonorm and whiskey are not the same thing. Which, is indeed true. (Although, he probably drinks a lot of whiskey).
Theoretically, in order to refute this argument, one would need to think of two objects that are actually identical, or 'one' and imagine a possible world where one of the objects exists and the other does not. This would show that the Cartesian argument is faulty since they were able to imagine object existing and the other not existing even though the two objects in question are
indeed the same object.
Critics of Descartes--and believe me, he has many--believe that they have done precisely that. A common argument they use against Descartes is that of a telephone and a ringing. They say that they could imagine a possible world where ringing occurs and the telephone does not exist and vice versa, thus, which would lead them by Descartes' logic to conclude that the telephone and the ringing are two different objects. The critics say that this is a false conclusion because they believe that the telephone and the ringing are
precisely the same thing as they both go along with each other, therefore Descartes' argument is false.
Apologists of Descartes' state that this refutation is faulty because it assumes that a telephone and the ringing from a telephone are not
the same thing, and to assume that they are is illogical. They assert that there is indeed a difference between an object and the function
of an object--in this case, the ringing which comes from the telephone. Therefore, it is not illogical to believe that the telephone and the ringing are two separate objects, therefore Descartes' argument still stands.
Essentially, it all comes down to a game of semantics. What is a telephone and what is ringing? When we use one of the words, what precisely are we referring to? When a critic refers to a telephone, they could be referring to both the object you hold to your ear and talk into, along with the ringing sound that it makes. While an apologist of Descartes could only mean the former when they say telephone. Therefore, this leads to confusion. Critics of Descartes can further argue that there is not
actually a difference between an object and the function of an object, because the latter cannot exist without the former, therefore, any 'possible' world where the function exists without the origin is actually illogical, and in turn, an 'impossible' world, or, in other words, utter nonsense, thus successfully refuting Descartes' argument.
What are your thoughts on this topic? As of right now, I find myself uncertain and undecided. I feel that I could easily defend and argue against each side.