Philosophical doubting of knowledge claims in various areas. From ancient to modern times, skeptics have challenged accepted views in metaphysics, science, morals, and religion. Pyrrhon of Elis (c. 360–272 BC) sought mental peace by avoiding commitment to any particular view; his approach gave rise in the lst century BC to Pyrrhonism, proponents of which sought to achieve suspension of judgment by systematically opposing various knowledge claims. One of its later leaders, Sextus Empiricus (2nd or 3rd century AD), strove for a state of imperturbability. Modern skeptical philosophers include Michel de Montaigne, Pierre Bayle, and David Hume.