With this paragraph Sextus Empiricus, the Greek sceptical philosopher, begins his introductory handbook to sceptical thought, the Outlines of Pyrrhonism. He portrays sceptics as perpetual students or researchers, as people who ‘persist in their investigations’, and the Greek adjective skeptikos derives from a verb meaning ‘to inquire’ or ‘to consider’. Now inquirers persist in their inquiries because they have neither discovered the object of their search nor concluded that it lies beyond all discovery: they have, as yet, no opinion on the matter. Hence the word skeptikos or ‘sceptical’ acquires its familiar connotation. Sceptics are doubters: they neither believe nor disbelieve, neither affirm nor deny.

To be sceptical on any given matter is to suspend judgement on it, to subscribe to no positive opinion either way.