for the most part known through his influence on Sextus Empiricus, and through the account of his teaching in Diogenes Laertius. A radical, he broke away from the Academy to return to the purer scepticism of Pyrrho. He is principally known for the ten tropes (tropoi) whereby we set up inconsistent but equally defensible claims about matters of fact. These tropes were canonized by Sextus Empiricus as the foundation of late Hellenic scepticism. They include

1. (i) the different ways different animals perceive things;

2. (ii) the differing perceptions of different peoples;

3. (iii) the way the different senses give differing judgements;

4. (iv) the ways in which circumstances such as drunkenness or sobriety affect perception;

5. (v) the differences brought in by distance and perspective;

6. (vi) the way in which the intervening medium (air, or the constitution of the eyeball) affects perception;

7. (vii) the way in which substances may look one way when combined and a different way when scattered or combined differently;

8. (viii) the pervasive influence of the specific relationship between the perceiver and that which is perceived;

9. (ix) the different importance and capacity for surprise that the same events assume for different perceivers; and

10. (x) the way in which differences between people prevent us from thinking of ourselves as perceiving universal moral laws.

A different set of eight tropoi put similar sceptical obstacles in front of knowledge of causal relationships. Almost all versions of scepticism and relativism rely upon some version of one or more of the ten tropes.