Perché Platone nel Timeo torna a sostenere la dottrina delle idee

In the whole Corpus Platonicum, we find in principle only one "direct argument" (Charles Kahn) for the existence of the ideas (Tim.51d3-51e6). The purpose of the article is to analyse this argument and to answer the question of why Plato in the Timaeus again defended the existence of the ideas despite the objections in the Parmenides. He defended it again because the latent presupposition of the apories in the Parmenides, the substantial view of sensibles, is removed through the introduction of space as "substantialized extension". First (I) it is shown that Plato remained in dialogues, like the Sophist and Politicus, faithful to the "theory of ideas" despite his criticism in the Parmenides. The common theme in the trilogy of the Theaetetus, Sophist and Politicus is to refute relativism by showing that any relativism presupposes something absolute that is something like the "theory of ideas". The second part of the paper (II) examines closely the logical structure of the argument for the existence of ideas in the Timaeus (51d3-52a7). The third part (III) shows how this argument can avoid the criticism of ideas in the Parmenides. In the Parmenides, sensibles are treated as substantial entities. But, as the Timaeus shows, sensibles are not substantial entities but merely qualities, namely qualities of space, which is the only substance in the sensible world. A shortened English version of the paper appeared in Proceedings of the Fourth Symposium Platonicum, Granada, Selected papers, ed. by T. Calvo/L. Brisson, Academia Verlag, St. Augustin, 1997, 179-186. But the only "direct argument" (Tim.51d3-51e6) seems to be interestingly flawed. Cf. Ferber, Rafael; Hiltbrunner, Thomas, (2005).