Towards the close of Book V of theRepublicPlato tells us that the true philosopher has knowledge and that the objects of knowledge are the Forms. By contrast, the ‘lovers of sights and sounds’, he tells us, have no more than belief, the objects of which are physical particulars. He then goes on to present us with some very radical-sounding assertions about the nature of these physical particulars. They are bearers of opposite properties, he says, in so thorough-going a manner that (...) we cannot say of them that they are nor that they are not: they lie somewhere between being and utter non-being.This passage of theRepublic still awaits an agreed interpretation and I want to suggest as a reason for this that it is usually interpreted in isolation. I will argue that it becomes easier to understand when seen against the background of Plato's developing thought. To be more precise, it makes sense when taken as a rejection by Plato of one of his earlier beliefs: namely, a doctrine of essentialism to be found in thePhaedo.The greater part of this paper then will be an attempt to show thatRepublicV is a rejection of thePhaedo'sdoctrine of essences. Its concluding part will try to explain why that doctrine was rejected. (shrink)