 In ancient times, skepticism had two main different forms: Pyrrhonism and Academic skepticism. Rediscovered in the Renaissance, skepticism became one of the pillars of modern philosophy, not only after modern skeptics, such as Michel de Montaigne, Pierre Bayle and David Hume, gave new impulse to it, but also because of the many answers to it developed by philosophers such as Francis Bacon, René Descartes, George Berkeley and Immanuel Kant. In the analytic tradition, from G. E. Moore and Bertrand Russell onwards, skepticism is a central topic of concern. This surprisingly long history shows not only how deep is the skeptical challenge, but also how fascinating the skeptical stance turns out to be.