This book presents a constructive interpretation of Plato's Parmenides . It offers a close reading of the dialogue's first part and shows how the second part takes up its problems while unfolding a philosophical project that reaches beyond them. The reader is guided through the exercise as Denis Walter shows how it articulates a complex ontology, addressing the hierarchy of forms, definitions, participation, mathematical structure, and teleology. By organizing the argument around philosophical topics rather than deductions, the study brings into view a coherent ontological framework extending from the One to unlimited multitude. The book offers a clear and philosophically grounded reading of one of Plato's most demanding texts.