Aisha asked:

Hey so I am stuck on a Philosophy question that states:

What is Descartes argument for the existence of the soul?

I have looked everywhere online and cannot find a simple yet understandable answer — could you help?

Answer by Geoffrey Klempner

Aisha, I am going to try to give a simple and understandable answer to your question. There is admittedly a problem with this, because what I find ‘simple’ or ‘understandable’ might not be so for you. I have to agree with you that many of the attempts I’ve seen are neither.

If I fail — my bad.

First, we need to explain the idea of identity. Everyone understands the idea of identity. Here’s an example: Batman IS Bruce Wayne. They are one and the same individual. They are identical. (According to Wikipedia, Batman is a fictional character created by Bob Kane and Bill finger. Batman’s first appearance was in Detective Comics #27, cover date May 1939, release date March 1939.) In real life, this kind of deception is pretty rare — that’s the only reason why I’m using a fictional example.

Let’s say that the Joker begins to suspect that Bruce Wayne is actually his hated enemy Batman. One night, the Joker ambushes Bruce Wayne and kills him. Shoots him full of holes, with no possibility of resuscitation. Let’s burn the body to ash, just to be sure.

The next day, ‘Batman’ foils a bank robbery. How do you and I know that the person who foiled the bank robbery isn’t really Batman? Because Batman and Bruce Wayne are the same person. If you kill Bruce Wayne, you kill Batman. If you kill Batman, you kill Bruce Wayne. The person who foiled the bank robbery can only have been someone wearing a ‘Batman’ costume, someone impersonating Batman. Because there IS no Batman. He’s dead.

So this was Descartes’ idea: can we imagine a possible scenario where my soul exists but my body does not exist? If I am just physical, then if my physical body dies then I cannot continue to exist.

Of course, we can always imagine some story about dying and going to heaven, but we’re trying to prove something. The story has got to be one that no-one could argue against. ‘I know I have a soul because when I die I will go to heaven,’ won’t work against an atheist who doesn’t believe in a place called ‘heaven’.

Here is the argument Descartes gave. It’s absolutely brilliant:

I know that I exist. That’s an absolute fact. I can’t think I exist when in fact I don’t exist, that would be nonsense. But I don’t know, not absolutely for sure, that I have a physical body. Maybe my entire life has been a dream. Maybe there is no physical universe. Maybe all there is, is just experiences, like the experiences I am having now, or the experiences you are having now.

You and I believe that we live in a physical world. Physical things exist. But the world might not have been a physical world. It is conceivable that there might not have been any physical things. But the thing I call ‘I’ would still exist in that non-physical world, and the thing you call ‘I’ would still exist in that non-physical world.

It follows that my ‘I’ and my body must be two things, they cannot be identical. Because if they were identical, then the very idea of my ‘I’ existing when my body did not exist would be absurd. It would be as absurd as thinking that Batman can exist even after Bruce Wayne has been murdered. As I have already explained, you and I know that if Bruce Wayne dies, Batman dies, and if ‘Batman’ subsequently appears, it can only be someone else wearing a Batman costume.

What is my ‘I’? We know that it is something that is not physical, because it can exist even in world where no physical things exist. Descartes calls it a ‘soul’.

But there’s a problem: if Descartes’ argument is so brilliant, why is it that most philosophers today aren’t convinced? Why do so many believe in the theory of materialism, according to which ‘I’ can only refer to something physical?

The biggest objection is to Descartes’ idea that it is ‘conceivable’ that the physical universe might not have existed and that all that existed was ‘just experiences’. That just doesn’t make any sense, these philosophers would say. It’s simply impossible. Or, if it isn’t impossible, it’s begging the question, by assuming that experiences can exist without physical bodies, brains, sense organs etc.

However, I still think there is mileage in Descartes’ idea, despite the objections. Because there is another way to run the argument about identity, which is in a way the reverse of what Descartes imagined. But it still relies on the same idea about identity.

Once again, the argument starts with the statement that I exist, and I know that I exist.

This time, instead of imagining that the physical universe might not have existed, I am considering the possibility that I might not have existed. The physical world could be just as it is now, with someone just like me answering this question on ‘Ask a Philosopher’, even though I did not exist and have never existed.

In other words, there’s a difference, an absolute logical difference, between me and someone exactly like me. But the difference isn’t a physical difference, it can’t be, because we are assuming that this person is physically like me in every detail, down to the fundamental constituents of matter. To make ‘someone exactly like me’ ME, something has to be added, something non-physical. In other words, a ‘soul’. Q.E.D.