of the most distinguished works of ancient scepticism that have survived. Sextus was a Greek who may have spent time in Rome and Alexandria, but little is known about his life, including where he was born and died. His works are divided into the Outlines of Pyrrhonism and Adversos Mathematicos (against the professors, or dogmatists). These works provide the main codification of Greek scepticism. Sextus defends a Pyrrhonian position whereby even the dialectic undermining the ‘trickster reason’ is eventually itself to be regarded quizzically: in his famous metaphor, it acts like a purgative, expelling itself along with the diseases it cures. His scepticism is confined to the adela or theoretical world beyond experience; central to his philosophy is the distinction between ‘indicative’ signs, which are signs taken improperly, as pointing to things lying beyond experience, and ‘commemorative’ or recollective signs, which are signs taken as symptoms of yet other signs, which are legitimate. The distinction anticipates the British empiricists’ difficulties in understanding how ideas can ever represent anything except by functioning as indicators of more ideas to come. Sextus’ writings include many central themes of these successors, including a distinction between primary and secondary qualities, and a view of causation similar to Hume’s. The aim of scepticism is to show how in life we must take appearances as they come, and the virtue of the sceptic is the imperturbability (ataraxia) with which he confronts the fact that this is all we can do. See also Aenesidemus, Carneades, Pyrrho.