Studies of Plato's metaphysics have tended to emphasise either the radical change between the early Theory of Forms and the late doctrines of the Timaeus and the Sophist, or to insist on a unity of approach that is unchanged throughout Plato's career. Professor Prior seeks to lay out an alternative approach. Focussing on two metaphysical doctrines of central importance to Plato's thought - the Theory of Forms and the doctrine of Being and Becoming - he suggests a continuous progress can be traced through Plato's works. He presents his argument through an examination of the metaphysical sections of six of the dialogues: the Euthyphro, Phaedo, Republic, Parmenides, Timaeus, and Sophist.

Introduction: the Problem of Plato's Development. Part 1: The metaphysics in the Early and Middle Platonic Dialogues 1. The Existence of the Forms 2. The Forms as Causes 3. The Forms as Paradigms. 4. Self-Predication 5. The Forms as Objects of Knowledge - the Being/Becoming Distinction 6. The Separation of Forms and Phenomena 7. The Problem of Participation. Part 2: The Challenge of the Parmenides 1. Socrates' Statement of the Theory of Forms 2. The Population Problem 3. Arguments against Immanence 4. The Third Man Argument 5. The Two-Worlds Argument 6. Conclusion. Part 3: The Response of the Timaeus 1. Being and becoming- the two Worlds 2. The Demiurge and the New Theory of Causation 3. The Forms as Paradigms 4. The Receptacle and Self-Predication. Part 4: The Sophist 1. The Critique of the Friends of the Forms 2. Plato's Account of Being and Not-Being 3. Paradeigmatism in the Sophist 4. The Timaeus and the Sophist - the Development of Plato's Metaphysics. Appendix: The Doctrinal maturity and Chronological Position of the Timaeus 1. The Ancient Interpretive Tradition 2. Stylometry. Bibliography. Index