Philosophical skepticism is both a philosophical school of thought and a method that crosses disciplines and cultures. Many skeptics critically examine the meaning systems of their times, and this examination often results in a position of ambiguity or doubt. This skepticism can range from disbelief in contemporary philosophical solutions, to agnosticism, to rejecting the reality of the external world.
One kind of scientific skepticism refers to the critical analysis of claims lacking empirical evidence. We are all skeptical of some things, especially since doubt and opposition are not always clearly distinguished. Philosophical skepticism, however, is an old movement with many variations, and contrasts with the view that at least one thing is certain, but if by being certain we mean absolute or unconditional certainty, then it is doubtful if it is rational to claim to be certain about anything. Indeed, for Hellenistic philosophers claiming that at least one thing is certain makes one a dogmatist.
Philosophical skepticism is distinguished from methodological skepticism in that philosophical skepticism is an approach that denies the possibility of certainty in knowledge, whereas methodological skepticism is an approach that subjects all knowledge claims to scrutiny with the goal of sorting out true from false claims.