We read Descartes to introduce the section on epistemology, the study of knowledge. Why? Because he raises an interesting question about what knowledge is.
Specifically, we seem to be forced to choose between:
- Our conviction that we know many things. For instance, I think I know what room I’m in and that it would be bizarre to say, “well, I’m not sure, but it looks like my office”.
- The equally solid point that we can’t know whether A or B is the truth if we can’t distinguish between them. For instance, I did not know that I had seen Emily on the street when I could not distinguish between Emily and Cynthia, her twin sister.
I don’t know which of those two to give up myself. Do you?
Descartes and Hume employ skeptical arguments. That means they try to show that we lack knowledge in a given area.
For instance, Descartes tries to show that without a foundation for our beliefs, we cannot be certain of what we believe on the basis of the senses. (We only got a start with what Descartes regarded as the foundations, with the alleged certainty that “I” exist. There’s more, but we aren’t reading it.)
Hume will try to show that we have no reason for drawing conclusions about what will happen in the future based on what we have observed in the past.
But, as Barrett appropriately asked, so what? What can you do with skepticism?
Some ancient skeptics thought that skepticism was a healthy thing. You could achieve peace or, at least, wisdom, by withholding belief from everything that is uncertain. And skepticism about some matters is sometimes a way of defusing conflicts. Skepticism about religious belief, for instance, might reduce the inclination to persecute non-believers.
Descartes and Hume used skeptical arguments in order to make other philosophical points. Descartes wanted to show what the foundations of our knowledge really are. He employed skepticism about the senses to show that our knowledge ultimately depends on God (in the parts we haven’t read). He also used it to show what we really are (intellectual, thinking things) as well as what bodies really are (extension).
Hume used skepticism about inductive inferences (our inferences about cause and effect relations based on past experience) in support of his psychological theory that the association of ideas explains our causal inferences. In the first paragraph of Section 7, you can see Hume aligning himself with the ancient skeptics. There, he argues that skepticism is a healthy alternative to what he sometimes called “enthusiasm”. What’s enthusiasm and why did Hume think poorly of it? An example will do better than any abstract description: enthusiasm is the frame of mind in which executing Thomas Aikenhead made sense.
On January 8, 1697, at some time between two and four in the afternoon, an eighteen-year-old student named Thomas Aikenhead was hanged in Edinburgh. Aikenhead had been found guilty of a serious charge: the previous year he had several times told other young men that the doctrines of Christian theology were “a rapsodie of faigned and ill-invented nonsense.” Aikenhead’s friends, testifying against him, told the court that he had spoken of “the Imposter Christ” and had rejected the Trinity, the Incarnation, and the Redemption. Aikenhead recanted all these sentiments—he said he had fallen under the spell of atheistical tracts—but no one defended him, and the jury voted for death.
Of course, it’s easy to be a skeptic about opinions that one doesn’t like. But what about those that seem necessary, like those involved in causal inferences? Hume wasn’t worried because he didn’t think that skepticism could result in giving up something as fundamental as causal inferences. The habits and customs are too deeply ingrained in us for that. So skepticism is both healthy and safe.
There’s a tendency to think that skeptical arguments are easy. You just ask “how do you know?”
But they’re not easy. I have a lot of evidence for many beliefs. I know that I’m not dreaming now because: my morning has been regular in ways that dreams aren’t, I can feel, hear, and see more things than I do in dreams, if I rap my knuckles real hard I don’t wake up, I can ask Peter if I’m really here and he’ll tell me, and so on.
By the same token, I have many reasons for thinking that I’m not a fictional character, a dog, or a teacup.
You have to be careful to set the argument up so that these common ways of knowing things are ruled out. That’s what Descartes, arguably, did with the deceiver argument. He might have done the same with the dream argument, but he didn’t. He should have taken Mike’s objection more seriously. That objection is that you know you’re not dreaming when you’re awake, even if you can’t tell the difference while you’re asleep. I can see how Descartes could have answered that, but he didn’t do so in the text.
Does Descartes know that he exists?
Yavor asked whether Descartes can know that he exists, by his own standards. I think it’s a good question.
Descartes’s answer has to be that it’s inconceivable that there could be an illusion without someone who is subjected to it. No thoughts without a thinker, no feelings without a feeler, and so on.
But do we know that those assumptions are true? Would it be more outlandish to doubt them than it is to doubt all the other things that Descartes thinks we can doubt?