Skepticism is the term for a philosophical attitude that fundamentally questions whether we can know anything at all. Despite the successes of modern natural sciences, this question reemerges in contemporary philosophy. It is precisely science that teaches us that the world is different from how it appears to us. Therefore, a skeptic asks whether it could also be different from how it appears to science. This question leads to the distinction between being and appearance, from which ancient skepticism originates and which reappears in modern skepticism. However, skepticism is not only about critical inquiries into claims of knowledge but also represents a way of life. If we cannot know anything, what should we do? This question must also be addressed by those who confront skepticism.