SCEPTICISM means in Greek philosophical (aKerroktat) usage to hesitate, to reflect, to examine, to consider pros and cons, to be unable to arrive at a decision or to rest content with surmise. Strictly defined, it is the denial of the possibility of knowing reality; that is to say, the human mind, by its very constitution, can never comprehend the ultimate nature of things. But this meaning belongs to the rarefied region of pure theory; so much so that complete denial has been the exception even among pro fessional thinkers. Hence the historical importance of the less stringent, even popular usage. For, in general acceptation, scepti cism suggests denial of current or customary beliefs. Its assault is by no means confined to theology, as is often supposed.
Taken thus as a repudiation of traditional or authoritative views, it tallies with the stricter philosophical definition in that historically, scepticism has flourished most during periods of transition when attacks upon previous systematic (or even com mon sense) constructions were rife. Obvious examples are fur nished by the assaults of the Sophists upon the Greek cosmolo gists; of Pyrrho and his pupils upon the followers of Plato and Aristotle ; of the Middle and New Academies upon Chrysippus and the Stoics ; of Sextus Empiricus upon all the principles of Graeco-Roman thought ; of Montaigne upon scholasticism ; of Glanvil upon the crusted Aristotelians of the Oxford schools ; of Locke upon certain aspects of Cartesianism ; of Hume upon Locke and the doctrine of representative perception; of Kant upon natural theology ; of L. Feuerbach upon Hegel; of agnostics upon the theological interpretation of nature and man; of Nietzsche upon the practical postulates of European Christendom; and of Pragmatism upon Idealism.
For philosophical thought and practical life alike, scepticism presupposes the existence of theories and socio-political situa tions which lay themselves open to attack. Accordingly, in the western world, it dates (c. 440 B.c.) from the Greek Sophists (q.v.) who not only impugned current cosmological speculations, but also impeached the ethical judgments peculiar to the Hellenic "city-state," Athens particularly. Their scepticism was general
rather than systematic, political as well as theoretical. Hence, the most thoroughgoing and persistent scepticism known to us arose with the profound changes wrought by Alexander the Great, the decline of the Hellenic type of civil polity, and the gradual ex haustion of original thought during the Roman Republic and Empire. Pyrrho of Elis (c. 30o B.c.), whose name furnishes the synonym for philosophical scepticism ; his pupil, Timon of Phlius (c. 25o B.c.) ; Carneades (c. Iso B.C.), above all Aenesidemus (c. A.D. 5o) and Sextus Empiricus (c. A.D. 20o) are the prominent figures. During the interval between the Sophists and Timon, scepticism was stayed by the personality of Socrates, and by the constructive systems of Plato and Aristotle.
Scepticism, as a distinct school, begins with Pyrrho of Elis, who maintained that knowledge of things is impossible and that we must assume an attitude of reserve (iroxi). The Pyrrhonists were consistent enough to extend their doubt even to their own principle of doubt. They thus attempted to make their scepticism universal, and to escape the reproach of basing it upon a fresh dogmatism. Mental imperturbability (IvrapaVa) was the result to be attained by cultivating such a frame of mind. The happiness or satisfaction of the individual was the end which dominated this scepticism as well as the contemporary systems of Stoicism and Epicureanism, and the three Schools agree that it consists in tranquillity or self-centred indifference. It is men's opinions or unwarranted judgments about things, say the sceptics, which betray them into desire, and painful effort and disappointment. From all this the man who abstains from judging one state to be preferable to another is delivered. But, as complete inactivity would have been synonymous with death, it appears to have been admitted that the sceptic, while retaining his conscious ness of the complete uncertainty enveloping every step, might follow custom in daily affairs.