Today we looked at several philosophers as they dealt with the age-old challenge of scepticism.
One way to divide up what we read is to think of different sceptical questions, which met with different answers from our philosophers.
A mild sceptic might say: “The senses deceive you sometimes. They deceive you, for example, in cases of illusion. Therefore you can’t trust them any of the time.” We saw Aquinas reply: “No, the senses don’t deceive us. If we see the sun in the sky, it looks small because it is at a distance. If we judge that the sun is small, we’re making a mistake in judgment, not in our senses. So if we control our judgements we will see that our senses do not mislead us at all.” But Aquinas is not very interested in the problem of scepticism.
An extreme sceptic might say: “You don’t know anything at all. Because you could be deceived about every single thing you think you know.” We saw Augustine replying that there is at least one thing he knows. Even if he is deceived, he knows that he exists. Our own existence can be known, whatever else is true.
A middling sceptic might say: “For all you know, the world could be totally unlike what you think it is.” Henry of Ghent gave a variety of arguments against the sceptic. Ultimately, Henry is willing to allow that there are things about which we are uncertain, because our knowledge of essences is assured by divine illumination. Still, he needs an argument against the sceptic. We looked at an argument he finds in Cicero, from the possibility of craft. Sceptics say we may not understand the world, but craftsmen act on the world and produce results in a reliable fashion. Doesn’t that prove that what the craftsmen do depends on true knowledge of the world?
One of the philosophers we read, Nicholas of Autrecourt, took the position of the sceptic. His argument, though somewhat complex in its exposition, boils down to this. Autrecourt’s former teacher, Bernard, said that the sceptic could never attack the principle of non-contradiction, i.e. The logical law that a thing and its contradictory cannot both be true at the same time. (For example, it can’t be raining and not raining at the same time, in the same way.) Now here’s Nicholas’ point. Bernard wants to go from the principle of non-contradiction to facts about substances (i.e. Natural things, like cats and people) and causes and effects. But all of those things are possibly different. In a science-fiction story, there might be different animals, and different causes, meaning that what is true here could be false, without contradiction. Since it could be false without contradiction, there’s no way for Bernard to have certainty about ordinary life, even if he can be certain of the law of non-contradiction!
Finally, we saw Jean Buridan (a contemporary and friend of Nicholas’), who tried to grant some of Nicholas’ point without being sceptical. Burden points out that, even if we grant the logical possibility that God could make things different, all we have to do is assume that God will act in regular and stable ways (not a huge surprise if God is rational and wants us to understand the world!). If we make that assumption, even though it’s not logically necessary that things in the future will go on the same way they have in the past, it’s still a safe bet.