From antiquity, Plato's Parmenides has been considered an enigma. In this book Robert Turnbull offers a translation and explanation of the Parmenides, using his interpretation to illuminate Plato's major late dialogues. Turnbull claims that in the Parmenides Plato abandoned the earlier Phaedo account of form-participation, and instead worked out the metaphysics of form-participation and mathematics that grounds the framework of his late philosophy. Relying on the testimony of Aristotle, Euclid, and Plotinus, and rejecting most modern accounts, Turnbull finds in the Parmenides a radical departure that that clarifies and illuminates Plato's mature Pythagoreanism. Until now there has been no standard modern interpretation of the Parmenides or of Plato's late dialogues. Professor Turnbull's book, with its meticulous translation and careful analysis, could well become that standard interpretation.