This paper explores the historical and palaeographical features linking together three manuscripts of Plato that bear - as previous researchers have shown - marginalia and textual corrections in the hand of the Byzantine humanist George Gemistos Pletho: Marc. Gr. 188 and 189 and Laur. 80, 19. There is, however, one more astonishing peculiarity associating precisely these three manuscripts: at several points there are erasures of passages dealing with ancient theology or with pagan myths and gods.The first part of this study (...) provides a general analysis of the censored passages, showing that they are part of a coherent project aiming at altering Plato's theology: in the manuscripts in his possession Pletho radically altered Plato's text, sometimes improving it, but sometimes censoring or entirely rewriting it; it is this very distinctive text of Plato that circulated in his school. In the second part, Pletho's acts of censorship as a whole are compared with his philosophical ideas as they can be reconstructed from the surviving portions of his Laws , proving that he tried to remove discrepancies between Plato and himself. In the third part of the essay, the ideological reasons for this censorship are investigated, with a special focus on the relations between Pletho's manuscripts and some miscellaneous codices belonging to his students or circulating in the platonic milieu of Mystra.The stemma codicum drawn up by Müller can thus be understood in its deeper cultural meaning, i.e. as an outline enabling us to understand how the philosopher propagated his ideas and to follow where and how they were received. (shrink)