There is a short argument at the end of Republicv (474b–480a) that demands a chapter to itself, so pivotal is it for the interpretation of Plato. One common reading has the argument making knowledge (epistēmē, gnōsis) and belief (or ‘judgement’, ‘opinion’: doxa) into two distinct faculties, with two distinct sets of objects: forms, on the one hand, and particular things that ‘share in’ forms on the other. On this reading, the person at the level of belief has no contact at all with the objects of knowledge, and the knower's knowledge relates entirely to forms; there will be no knowledge, properly speaking, of particulars, and perhaps there will even be no mere beliefs about forms (either one fully grasps such objects or one is not grasping them at all). A whole range of different versions of this set of ideas – usually labelled the ‘two-world’ view – is attributed to Plato; however, following my usual practice, I shall dispense with lengthy discussion of others' views and pass directly to the business of presenting and arguing for my own.

The reading I shall offer in this case will not in its general outlines be particularly original (my route to it will be more so); my aim is chiefly to show that and how my overall reading of Plato will negotiate a passage to which interpreters have accorded such importance – rather more, I suspect, than Plato would have accorded it himself, and more than it possesses for Socrates in the context in which he unfolds it.