Putting Descartes Before the Horse
So Rene Descartes walks into a bar. Some guy walks up to him, says, “Hey, aren’t you one of those skeptics we keep hearing about on the news?” Rene, indignant, replies, “I think not!” — and promptly disappears in a puff of logic.
All right, you now understand why so-called philosophical humor only appeals to people who have spent way too much time reading academic journals. But if all you know about Descartes is the famous “I think, therefore I am,” stick tight for a second, because I want to talk about why the thought process that led to that declaration is still so important today.
Descartes was a scientist and a mathematician as well as a philosopher, and he was tremendously concerned by the skeptics. They’re the people who go around challenging all claims to knowledge for one reason or another, saying there was no reason to be certain about anything. If you couldn’t be certain that the discoveries of science were true, was there still a point in the endeavor? And if you couldn’t be sure about the life you were living at the moment, how could you be sure about what happen in the next one? Skeptics challenged the authority of both scientists and the Church, and this was something Descartes desperately wanted to avoid.
So he set up a thought experiment, detailed in his book Meditations on First Philosophy. “Anything that I can possibly call into question, anything about which I can raise the slightest doubt, I’m going to assume is false.” That’s a tough — and potentially impossible — standard; there’s a reason we require criminal cases to be decided beyond a reasonable doubt and not beyond all doubt. But Descartes believed that if he could find anything that met that standard, he could rebuild the rest of human knowledge on that foundation, and send the skeptics home with their philosophical tails between their legs.
At first, it looks like he might run into trouble. We’ve all had experiences where our senses seem to deceive us — optical illusions, hallucinations, dreams, and so on. Furthermore, Descartes says, there’s always the possibility that God or some all-powerful entity is playing a cosmic joke at our expense, deceiving us about the nature of the world around us. This is the possibility of the evil genius, which was later modified by philosophers into the brain-in-the-vat hypothesis, which suggested that since sensations seem to be caused by signals sent to the brain, someone could conceivably remove my brain from my body and trick it into thinking it were still in my body. In the last year or two, this has been modified yet again into the “Matrix scenario,” which says that it’s not impossible that I wake up tomorrow to find Laurence Fishburne wanting to teach me kung fu. No matter how you describe it, we seem to be able to come up with some fantastic scenario that would mean Everything We Know Is a Lie — and as long as that’s possible, the skeptics win.
But then Descartes pulls out the trump card. No matter what scenario you come up with to describe how I’m being tricked, the fact remains that I’m being tricked. I have to have some sort of thinking process going in order to process the information and form my conclusions; even if the conclusions are all dead wrong, there’s no way to deny I’m having them. So as long as I’m thinking about things, even if I’m being deceived, I can rest assured that I exist — if I didn’t exist, I wouldn’t have been able to kick off the whole thought experiment in the first place. So we get the famous statement cogito ergo sum — I think, therefore I am.
Here’s the thing, though — all we’ve proven so far is that some nebulous thinking thing called me exists. Do I have a body? Is that body even remotely like the body I think I have? (Imagine if Keanu Reeves had woken up and found out that he was really a twelve-foot-tall amoeba-like creature. Whoa.) I could exist and be hallucinating or imagining everything else, including the people I think I’m having conversations with and the computer I think I’m using to talk to them. This position — that nothing other than myself exists or can be shown to exist — is called solipsism, by the way. Defeating solipsism is one of the major challenges philosophers have to face in trying to figure out how our minds connect to the world outsider us.
Descartes eventually, through a somewhat tortured reasoning process that I might get into on the message boards, establishes that we can in fact be confident that we have bodies and that what our senses tell us is generally accurate. But he also argues that the body is not fundamental to who we are — at the most basic level, we are those amorphous thinking things and nothing more. Right now, we happen to be attached to those physical things, but later on, we’ll shed them and move on, no worse for wear. Descartes, therefore, is a mind-body dualist, because he believes the mind and the body are two separate, independent substances and entities.
Now, this is where we run into some problems. Today, we often tend to assume that the physical universe is causally closed — that anything that happens can be explained by looking at its physical causes. If I have one force pulling an object north, and another force of equal strength pulling the object south, we’re supposed to be able to know that the two forces will cancel out and the object will remain stationary. If we see the object moving south, we are supposed to be able to know that there’s a stronger force pulling it that way. So if everything that happens in the physical world is a result of prior physical causes, and my body is a thing in the physical world — how does my mind give it instructions and have any effect on it? And how do things that happen to my body — like lack of sleep, physical disorders, or certain kinds of drugs — effect the way I think and feel, if the mind is somehow distinct from and independent of the body? If you say the physical universe isn’t causally closed, you’re going to have to start rewriting all those formulae that describe things that occur in the body in purely physical, mechanistic terms. If you say it is causally closed and that the mind is a whole different kind of substance, you’ve turned the mind into an ineffectual passenger riding along inside the body. This is why mind-body dualism raises a host of questions, some of which — like “What does it mean to be human?” and “Do human beings have free will?” — we’ve already begun to discuss on the message boards.
Philosophers have spent hundreds of years grappling with the questions Descartes’ writings pose, and it’s only in the last hundred years or so that we’ve begun to realize that maybe the real answer lies in rephrasing the questions. Over the next several Philosophy updates, we’ll move through that process — so stay tuned.
About Dave Thomer
Born and raised in Philadelphia. Studied philosophy at Fordham University in the Bronx, where I made many great friends and met my wonderful wife. We moved back to Philadelphia, where I studied philosophy some more and became a teacher. Online and off, I'm looking for ways that we can be better citizens and build stronger communities.