 The major tool we're going to be talking about is skepticism, but skepticism really has two different forms and we have to distinguish two forms of it, and in a way there isn't one thing called skepticism. Now the term here doesn't come from the name of the founder or from the place where it was founded, but rather skepticism is a description of the activity of this philosophy. So it comes from this Greek word skeptis, which means inquiry, investigation, examination. And if you're a skeptic, you're someone who thinks that we need to keep investigating this issue. It's not resolved and we need further research on it. And there are two forms, academic skepticism and Peronian skepticism, which we'll be going into detail. We'll have dedicated days discussing both of those. The essential difference is that according to academic skeptics, knowledge is impossible. You cannot gain knowledge. Whereas Peronian skeptics go even further and say we can't know even that knowledge is impossible. So we need to keep actually researching and investigating the issue of whether knowledge is possible. So although it looks like academic, it's hard to tell which of these is the more radical view, the one that says knowledge cannot be had at all, or the one that says we can't even know whether we can have knowledge at all. Now, their views differ in each of these categories and we'll give a sort of synthetic account of them in logic. The academics try to pick apart all claims to knowledge, especially those among the Stoics. And they were involved in a multi-century dialectical battle with the Stoics. The Stoics claiming we can actually obtain knowledge from certain kinds of inferences that we can make from sense perception and other logical means. Peronians don't just try to combat views like the Stoics. They will also research and use Stoic views against other schools. So if they're arguing against Epicureans, they'll deploy Stoic arguments. And if they're arguing against Stoics and they'll deploy Epicurean arguments, they'll deploy any sort of argument for the purpose of suspending judgment on whether the position arrived at is true or not. So the goal is to get your mind in a position where you do not commit to either view. Now, in both cases, they themselves have a physical system. They reject all dogmatic forms of physics. So they reject the idea that everything consists of atoms and void, and they reject the view that no, everything is continuous and there's one cosmos. For ethics, academics essentially reject dogmatic ethics, especially Stoic ethics. Peronians claim that tranquility is the end of our life. What we really want to do is not be bothered by things. So, essentially, it's even more important than not having pain in your body that you don't have anxiety and mental illness in your mind, that they think that you can achieve that end just happens to follow from suspending your judgment on everything. That once you're able to do that, to master these skeptical techniques of counterbalancing any particular argument for any view and then suspending your judgment about it, you get this nice, cool, calm, relaxed feeling where you're not stressed out anymore. So you're stressed out because Epicureans are saying, hey, the whole point of life is pleasure and you realize I'm not really enjoying life, so I'm not really achieving the whole end of life. Or the Stoics are saying, no, the whole point is to be a virtuous person and you're thinking, I'm not actually a very virtuous person, I'm not very courageous and I don't have much self-control, so you're stressed out about this. So what you do is you go to a skeptic who says, look, neither of these views are correct. There's no solid reason to think that pleasure is the end of life, so you're probably not really missing out on much by not having a pleasant life. And furthermore, there's really no reason to think that these highfalutin virtue things that anybody needs to pursue, those to be happy. So stop worrying about that and consider all these arguments that go against that. And then when you accept all of that, you realize, well, I don't even know if anything's good or bad by nature and you get this calm, relaxing, tranquil feeling. And that's the point of that kind of skepticism. One thing that's really interesting about ancient skepticism is that the idea is that the result is supposed to be this feeling of tranquility. It's a lot different than modern skepticism. And modern skepticism and Descartes and Hume and these forms, it's like you're imagining that an evil demon could be deceiving you at every moment or that the entire external world might disappear and it's this really terrifying thing. And this always struck me that modern skepticism is a scary anxiety-producing thing that we've got to try to answer or something, whereas in the ancient version it was this tranquil feel-good philosophy. Okay, and Peronian skepticism is named after this Socrates-like figure, Piro, who advocated suspension of judgment about everything, including whether anything was by nature good or bad. But this led him to do crazy things like not avoid precipices or oncoming cars because he didn't know, is that good or bad to avoid that? Is it good or bad to continue living? I don't know, I suspend judgment about it. But fortunately, his students would sort of, as he was about to walk up a cliff, sort of crowd him and say, you know what I mean, and say he did not face. But he didn't write anything. Like Socrates, he just inspired other people through these views that he expressed orally and through his behaviors. Hundreds of years later, though, this crystallized into a philosophy called Peronian skepticism, which is in the works of sexist empiricus and Alexandrian philosopher who wrote several works, including a three-book outlines of skepticism and another 10 books called Against the Professors that have these great titles like Against the Logic Professors, Against the Physics Professors, Against the Ethics Professors, but then he even goes further, Against the Grammar Professors, Against the Mathematics Professors, Against the Music Professors. He goes through every single purported claim to knowledge. And so he gives a kind of conspectus of the whole of ancient science and what grounds there are for skepticism about any of it. And it sounds like a crazy thing to do, but we're pretty skeptical about ancient claims of science. So maybe there is really something to what he was doing. And of course, Peronian skeptical techniques are still employed.