Various forms of skepticism play important roles in the history of philosophy. Do we really know there are external objects? That there are other minds? That there is a distant (or even a not-so-distant) past? All the evidence we have for these things seems consistent with our being in a world in which they don’t exist. What does this tell us about life? About philosophy? Our hosts discuss one of the deepest and most fertile philosophical traditions with John Greco from St. Louis University, editor of The Oxford Handbook of Skepticism.