Let’s look at where we are in this course: we started off with whether God exists, then moved on to discussing individual ethics, and then the structure of society. The first unit dealt with one big question of what there is in the world, and the second two dealt with what we ought to do. Now we’re going to move back to questions of what there is in the world.

But note there’s another way I’m organizing the class: I tried to start out with issues most likely to come up in the popular press and casual conversation. Religion, ethics, and politics aren’t things you talk about if you’re worried about offending someone, but they’re common choices if you’re looking to start an argument. Today, we begin the move to less familiar topics, though this one is only a little less familiar: the nature of the human mind, including questions about the soul and free will.

Okay, where do we begin? There’s a philosopher who teaches at the University of Notre Dame, Peter van Inwagen, who’s done a number of things I really like. One is coin the phrase “Hollywood-and-Notre-Dame-undergraduate picture,” referring to a sort of common sense view of the mind and body. The view is this: you have a body and a soul. Normally, your soul is in the same place as the body. When you die, though, the soul rises up out of the body. Normally, the soul is invisible, but if you manage to see a soul somehow it will look exactly like the body of the person it belongs to. Not only is a disembodied soul invisible, but under ordinary conditions it doesn’t interact with things in any other way. Physical objects pass right through it. However, an especially angry ghost might be able to make a vase go crashing to the floor. The mental characteristics of a disembodied soul will be similar if not identical to the embodied version. In a living person, the soul controls the body, and is central to providing the body’s mental characteristics.

As a simple matter of historical fact, I don’t think any major philosopher has accepted the Hollywood-and-Notre-Dame-undergraduate theory of the mind. However, there is one very important philosopher who believed something at least a bit similar: Rene Descartes. For those who care, Descartes lived from 1596 to 1650, and invented coordinate geometry–you know, the whole x-axis, y-axis deal. Descartes agreed with Hollywood that you have a body and soul, and the soul is what is your mind, and controls the body. He disagreed with Hollywood in that he didn’t think souls were extended in space, and the soul isn’t even located in space. So, your soul isn’t exactly as tall as you are, says Descartes, because it doesn’t have a height, and when you die it won’t leave the hospital through the roof.

Be warned that while Descartes aligned himself with the Catholic Church (even though they didn’t like everything he said), and while Descartes views have become popular among sophisticated religious thinkers who want to give an account of the afterlife, they aren’t the only religious option out there. Thomas Aquinas, as I understand him, didn’t have Descartes’ view of the mind. I’m not sure I understand Aquinas’ view, but it was a modified view of Aristotle, who thought that the soul was the form of the body. This was supposed to be analogous to the relationship between the form of a statue and the marble composing it. I’m not sure I understand Aristotle’s view, either, but be aware that non-Cartesian religious views are out there. Incidentally, Peter van Inwagen is a Christian example. Van Inwagen denies that there are souls, and thinks the afterlife is all about being risen miraculously from the dead. You can find this diversity of views far back in time. Read Josephus, who was the main Jewish historian who wrote about roughly the time of Jesus, and you’ll get an account of three different views of the afterlife held by the different Jewish sects at the time: the Pharisees, the Sadducees, and the Essences. Now, you won’t be tested in-depth on Aristotle or Aquinas or van Inwagen or Roman-era Palestine, but you should be aware that non-Cartesian but religious views are out there.

Now that I’ve given you these basics, I want to give you a sort of standard philosophy-class story about why anyone would be a Cartesian, and why they’re wrong. It seems like everyone gets this story in introduction to philosophy, so I’m giving it to you, too, but I’m also going to give you some cautions about it.

First, why did Descartes believe the mind was distinct from the body? The argument attributed to Descartes goes like this:

(1) I can doubt the existence of my body
(2) I can’t doubt the existence of my mind
(3) If two things have distinct properties, they are distinct things
Therefore, my mind and body are distinct.

Three assumptions go into this argument. Where do they come from? The first two are some ideas Descartes had that I don’t want to say too much about until later, but here’s the basics. I look at my hands, and I have to admit maybe, they could be a hallucination. There are actually people who, in a sense, have hallucinated limbs, though they’re not visual hallucinations but feeling hallucinations. It’s called phantom limbs: they loose a limb but it still feels like they have it. On the other hand, Descartes says, we can’t doubt the existence of our minds, because if we try to doubt that, there has to be an us to do the doubting, a mind to do the doubting.

There are some important ideas about the nature of reason and knowledge in there, but let’s try to side step them. One approach is just to say that there’s a gap between our ability to imagine not having a body, and our ability to imagine not having a mind. Or, perhaps, the argument is we can imagine ourselves as disembodied minds.

What about the third assumption? The idea is we have to account for inferences like this:
(1) John is a philosophy teacher
(2) Jones is not a philosophy teacher
(3) Link???
Therefore, John is not Jones.

Standard reply to Descartes: this sort of principle works, but only with cases not involving intensionality. What is intensionality, you ask? Simple definition: it’s “aboutness”: things like doubting, believing, knowing, liking, wanting. Some standard examples of where an argument doesn’t work, because of intentionality:

(1) I know that the masked man is in the room
(2) I don’t know that my father is in the room
It DOES NOT follow from this that I know the masked man is not my father

(1) Lois Lane wants to kiss Superman
(2) Lois Lane doesn’t want to kiss Clark Kent
It DOES NOT follow from this that Superman is not Clark Kent (though you have to wonder why there’s any confusion, given that Supes doesn’t wear a mask).

This is the standard story about why Descartes didn’t have a good argument for his dualism. Is the criticism correct? Well, what quite a few philosophers would say today that maybe Descartes stated the argument badly, but suspect there’s something like Descartes’ argument that works. Since that takes us away from Descartes into the contemporary era, I’m going to leave it aside for next lecture. Something to work forward to.

Next question: suppose we accept that Descartes couldn’t show he was right about the mind, can we show he was wrong? Here’s one story about why Descartes’ views have been rejected: on his account, the mind and body are so wildly different that there’s no way for them to interact. I want to give you an exact quote propounding this view, originally from Antony Kenny, though I myself got it from one of Jaegwon Kim’s books:

On Descartes’ principles it is difficult to see how an unextended thinking substance can cause motion in an extended unthinking substance and how the extended unthinking substance can cause sensations in the unexteneded thinking substance. The properties of the two kinds of substance seem to place them in such diverse categories that it is impossible for them to interact.

This looks like a clear bit of prose, and if you find it confusing I’m sorry to say I can’t help you, because I don’t understand it either.

Realize that in the 20th century, it was popular to claim that this was the actual historical reason for the historical downfall of Cartesianism. Also realize that historically, that may not be right. Here, for example, is the objection to Cartesianism lodged by Leibniz, inventor of calculus:

Descartes recognized that souls cannot impart any force to bodies, because there is always the same quantity of force in matter. Nevertheless he was of opinion that the soul could change the direction of bodies. But that is because in his time it was not known that there is a law of nature which affirms also the conservation of the same total direction in matter.

You may or may not know from high school physics the principles Leibniz is talking about. If not, it’s OK, the main idea is that Leibniz claimed Cartesianism was consistent with the physics of Descartes’ day, but not the physics of Leibniz’ day, half a century after Descartes. And Descartes himself worried about questions like what part of the body’s anatomy was the site of interaction with the soul. He once proposed this happened at the pineal gland, though later realized perhaps this wasn’t his brightest idea. The historical reasons for Descartes’ fall were to an important degree scientific, again something I’ll say more about next time.

Back to the standard philosophy class story. One suggestion as to what the real problem is, is that we don’t the faintest idea what the mechanism might be, by which the mind affects the body. For example, we know the molecular biology and physiology of digestion. The thought is we should have something like that for mind-body interaction, if such a thing is real.

But wait a minute. Do we always have a mechanism? We can break digestion down into steps, but can we give a mechanism for every step? If we have one for every step, do we have one for every sub-step? Is there a mechanism by which the electrons and nuclei of one molecule affect those of another molecule? If we say the mechanism is one of electric fields, do we have a mechanism for electric fields? At some point, explanation has to stop, and we just accept that interaction happens, without having a mechanism.

Jaegwon Kim, I said, is the philosopher I got the Antony Kenny quote from, and Kim is suspicious of Kenny’s argument. However, Kim isn’t a friend of Cartesianism, so Kim tries to give another critique of Cartesianism in place of Kenny’s. Kim’s idea is this: consider a case where two people are shot and killed at the same time by two bullets of two different guns (maybe they were both convicted of being part of the same plot). What makes it true that shot A killed victim A and shot B killed victim B, rather than the other way round? For Kim, he key is that you can trace a causal path from each gun to the assigned victim. If not for that, there would be no basis for associating one gun with one dead man and the other with the other. Kim generalizes from this to say that all causation requires spatial relation. Since Descartes’ souls aren’t located in space, they can’t participate in causal relations.
I’m not sure this is much of an improvement over Kenny’s argument. Imagine a universe where maybe there is nothing not located in space, but occasionally particles become somehow connected with each other, so that whenever you spin one, the other spins, and this connection stays fixed no matter how far you separate the particles. Do we want to say that such a world is impossible? That we can prove such a world is impossible by metaphysical argument? I can’t endorse that view, but it would have to be impossible for Kim’s spatial account of causation to work. Therefore, I can’t endorse Kim’s conclusion.

Next time, we’ll try to move away from this and towards arguments inspired by modern science.