ABSTRACT
Skepticism is a philosophical attitude that questions the reliability of, or even the possibility of acquiring, knowledge about the world. Tracing their origins to ancient Greek philosophy, skeptics argue that neither the senses nor a priori reasoning are reliable sources of knowledge about the world. In the classical world, Academic skeptics concluded that we can know nothing, while Pyrrhonian skeptics questioned whether we can even know whether we know anything. Both schools argued that knowledge about the world can never be certain.
