Cartesian Skepticism

Welcome to the blog’s first foray into epistemology: the philosophical study of knowledge. Today we will be talking about René Descartes, who will be ensconced in infamy for two feats: creating a system of geometry that would annoy high school students for hundreds of years to come, and for presaging “The Matrix”. Much as I actually liked high school geometry, I would like here to talk about the Cartesian skepticism of the external world that made so many science fiction movies possible.

For those of you who haven’t yet read Descartes’ famous Meditations on First Philosophy (mostly referenced plainly as the Meditations), what are you waiting for? Here’s an old translation into English to get you started. There are also approximately a billion print versions available on Amazon, in case you want a more contemporary translation, along with the ability to scribble in the margins.

The Meditations start with Descartes recounting the none-too-astounding realization that he had been wrong about some things as a youngster.

Several years have now elapsed since I first became aware that I had accepted, even from my youth, many false opinions for true, and that consequently what I afterward based on such principles was highly doubtful; and from that time I was convinced of the necessity of undertaking once in my life to rid myself of all the opinions I had adopted, and of commencing anew the work of building from the foundation, if I desired to establish a firm and abiding superstructure in the sciences.

So his project in the Meditations was very much foundational. Descartes wanted to tear down all things that passed for knowledge, in order to find a kernel of certainty, from which he would build back up a magnificent structure of infallible knowledge. Those of you who remember high school geometry might be having nightmarish flashbacks at this point, remembering how the subject was built up from just a few, allegedly very certain axioms. The axioms were the firm, unassailable foundation upon which the science of geometry was built. Descartes had similar plans for every other science and in fact every human epistemological endeavor.

His method was, simply enough, to sit comfortably in his pajamas and begin doubting everything that he possibly could doubt. The first victim of his skepticism was his senses. “All that I have, up to this moment, accepted as possessed of the highest truth and certainty, I received either from or through the senses. I observed, however, that these sometimes misled us; and it is the part of prudence not to place absolute confidence in that by which we have even once been deceived.” A pretty reasonable place to start doubting things. After all, there are a million and one ways in which we are regularly deceived by our senses: optical illusions abound, hallucinations occasionally crop up, and physical ailments of the eyes and brain can cause misperceptions.

But there’s an even more radical skepticism that can crop up from this line of thought. What if it’s not just the case that the senses deceive, but that they don’t exist at all? Take this picture of the human knowledge machine:

Beach ball on the inner screen

On this picture (which, I think, is a pretty sound depiction of what philosophers of that age thought, and indeed is still how a lot of people picture the mind), the only reliable access to knowledge is via an inner screen that has projected upon it images of the external world. The screen here is inside the brain/mind, and the little person viewing the screen is one’s consciousness. If the senses exist, then sometimes they project something misleading on the inner screen, and this gives rise to optical illusions and hallucinations. But on this picture, a skeptic could go so far as to say that the senses might be fictional. If all we have access to is this inner screen, then we just can’t be sure from where its images come. Maybe they come from the senses, and maybe they don’t. Of course, given that there were really no computers or any decent science fiction at the time, the only 17th Century source that would be powerful enough to accomplish this illusory feat would be God. But since God is supposed to be omnibenevolent, and would therefore not deceive us in this way, Descartes conjured up a reasonable facsimile of sci-fi for the time, and said that perhaps there is an evil demon who deceives each of us in this way.

Evil Demon at work deceiving us

Well, that’s a lot of doubt, and a lot of the world’s furniture that has suddenly become dispensable. Stones, trees, and cats might not exist. Neither might other people, for that matter. Descartes found himself at this point in an extremely solipsistic position. He might be the only person in the universe. And this person might not even have a body.

At this point, Descartes took some certainty back from the skeptical vortex into which he was falling. He might not have a body, but if he was indeed being deceived by some evil demon, then he was being deceived. “I am, I exist,” he concluded. And each time he thinks this (or anything else, for that matter), his existence is assured.

At this point, we could veer off into metaphysics and the philosophy of mind, and discuss the ontological corollary to this barely optimistic offramp of the Cartesian skeptical superhighway: Dualism. According to Descartes’ theory, the mind is not necessarily connected to a body; that is, it is logically possible for a mind to exist without a brain.

But let’s save this subject for another post. Now, let’s examine where Cartesian skepticism has taken us, epistemologically.

Skepticism of the external world is a very strong philosophical position. It is really quite difficult to debate a skeptic on matters of epistemology, because the default answer of “but can you really know that the external world exists” is very defensible. Try it out for yourself:

Me: This iPhone is great.
You: If it exists.
Me: What do you mean? I’m holding the thing in my hand!
You: You think you are. Maybe you’re dreaming.
Me: I know the difference between a dream and reality.
You: You think you do. But maybe you’re in a dream, and in that dream you dream that you’re awake, but really you’re still just dreaming.
Me: Oh, come on. That leads to an absurd infinite regress of dream states.
You: Well, it’s still possible. And anyway, you could be living in a computer simulation. Or you could be crazy and hallucinating all of this. In any event, you can’t know for sure that you’re holding an iPhone in your hand. You can know that you have an image of holding an iPhone in your mind. Therefore your mind exists. Does that make you feel better?

And you have won the debate!

The Way Out

So do we have to just give in to the skeptic? Is there no hope for those of us who would like to assume the existence of stones, trees, and cats? Real ones… not just images of them in our minds.

Well, yes, there is. It’s called Naturalized Epistemology (or just “naturalism”), and it was foreshadowed by David Hume way back in 1748. I’ll quote a lengthy passage, because it’s so beautifully crafted:

For here is the chief and most confounding objection to excessive scepticism, that no durable good can ever result from it; while it remains in its full force and vigour. We need only ask such a sceptic, What his meaning is? And what he proposes by all these curious researches? He is immediately at a loss, and knows not what to answer. A Copernican or Ptolemaic, who supports each his different system of astronomy, may hope to produce a conviction, which will remain constant and durable, with his audience. A Stoic or Epicurean displays principles, which may not be durable, but which have an effect on conduct and behaviour. But a Pyrrhonian cannot expect, that his philosophy will have any constant influence on the mind: or if it had, that its influence would be beneficial to society. On the contrary, he must acknowledge, if he will acknowledge anything, that all human life must perish, were his principles universally and steadily to prevail. All discourse, all action would immediately cease; and men remain in a total lethargy, till the necessities of nature, unsatisfied, put an end to their miserable existence. It is true; so fatal an event is very little to be dreaded. Nature is always too strong for principle. And though a Pyrrhonian may throw himself or others into a momentary amazement and confusion by his profound reasonings; the first and most trivial event in life will put to flight all his doubts and scruples, and leave him the same, in every point of action and speculation, with the philosophers of every other sect, or with those who never concerned themselves in any philosophical researches. When he awakes from his dream, he will be the first to join in the laugh against himself, and to confess, that all his objections are mere amusement, and can have no other tendency than to show the whimsical condition of mankind, who must act and reason and believe; though they are not able, by their most diligent enquiry, to satisfy themselves concerning the foundation of these operations, or to remove the objections, which may be raised against them.

So, the idea (if you had a hard time navigating the old-school English), is that if skepticism of the external world is true, it leaves one in the unenviable position of nothing mattering. It is not a stance from which one can do any productive theorizing about science, philosophy, or, well, anything except for one’s own mind. (And even that bit of theorizing will stop at the acknowledgement of one’s inner screen accessible to consciousness.)

Do we have a stance from which we can do productive theorizing about things? Assuming that science is generally correct about the state of the world is a good start! After all, science has some of the smartest people in the world (if they and the world exist) applying the most stringent thinking and experimentation known to humanity. And science assumes the existence of things like stones, trees, and cats — things that exist in the world, not merely as ideas in our minds.

Here’s one of the more interesting perspectives on subverting skepticism, from Peter Millican at Oxford:

The gist of the video is that there are two ways to argue every issue. In the case of skepticism of the external world, you can argue, like a naturalist, that you know that stones, trees, and cats are real, therefore you know that there is an external world; or, like a skeptic, you could argue that we don’t know that there is an external world, therefore you don’t know that stones, trees, and cats exist. They are really quite equally plausible strategies, from a strictly logical point of view. And in both cases you have to assume something to be the case in order to get to your desired conclusion. So do you want to assume that you don’t know there’s an external world, or would you rather assume that you know that stones, trees, and cats exist? Your choice.

If you choose the skeptical path, I hope you’ll choose to pass your solipsistic time entertaining dreams of this blog.

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