AGRIPPA  , a sceptical philosopher, whose date cannot be accurately determined . He must have lived later than

Aenesidemus, who is generally said to have been a contemporary of Cicero . To him are ascribed the five tropes (7Evm epoaoi) which, according to Sextus Empiricus, summarize the attitude of the later ancient sceptics . The first trope emphasizes the disagreement of philosophers on all fundamental points; know-ledge comes either from the senses or from reason . Some thinkers hold that nothing is known but the things of sense; others that the things of reason alone are known; and so on . It follows that the only wise course is to be content with an attitude of indifference, neither to affirm nor to deny . The second trope deals with the validity of proof; the proof of one so-called fact depends on another fact which itself needs demonstration, and so on ad infinitum . The third points out that the data of sense are relative to the sentient being, those of reason to the intelligent mind; that in different conditions things themselves are seen or thought to be different . Where, then, is the absolute criterion ? Fourthly, if we examine things fairly, we see that in point of fact all knowledge depends on certain hypotheses, or facts taken for granted . Such knowledge is fundamentally hypothetical, and might well be accepted as such without the labour of a demonstration which is logically invalid . The fifth trope points out the impossibility of proving the sensible by the intelligible inasmuch as it remains to establish the intelligible in its turn by the sensible .

Such a

process is a vicious circle and has no logical validity . A comparison of these tropes with the ten tropes enumerated in the article AENESIDEMUS shows that scepticism has made an advance into the more abtruse questions of metaphysics . The first and the third include all the ideas expressed in the ten tropes, and the other three systematize the more profound difficulties which new thinkers had developed . Aenesidemus was content to attack the validity of sense-given knowledge; Agrippa goes further and impugns the possibility of all truth whatever . His reasons are those of modern scepticism, the reasons which by their very nature are not susceptible of disproof . See Diogenes Laertius x . 88, and Zeller's Greek Philosophy . Also the articles SCEPTICISM; AENESIDEMUS .