Byzantine philosopher (c. 1360-1454), perhaps the most important of late Byzantine period. He received a good theological and philosophical education, he knew Latin and he was possibly familiar with Judaism and Islamic thought; as a teacher he had prominent students as Bessarion. He served as advisor to Byzantine rulers of Mistra, suggesting social and political reforms. He participated in the Council of Ferrara-Florence holding anti-unionist stance.

The philosophical and scientific work of Pletho is important, as well as his impact on Greek scholars and Italian humanists. Pletho was well aware of the Platonic work and was influenced by its Neoplatonic interpretation. He considered Plato as the most important of a long chain of ancient sages because in his thought is recorded in the best philosophical way the revealed primordial truth.

In his great work Book of Laws he establishes the perfect state of the Greek nation (genos) on a metaphysical and moral basis constructed by (Neo)platonic material. The state proposed is inspired by Plato, has a tripartite structure and is a kind of enlightened monarchy. It is based on a rational religion that combines a peculiar Neoplatonism with ancient Greek mythology and uses metaphysical concepts to display the polytheistic pantheon and strict henotheistic hierarchy. At the top lies Zeus: the One beyond of substance, the idea of Good, eternal and ultimate cause of everything. The reason is the criterion of all and through it we accomplish truth and happiness; necessary conditions for their accomplishment are the knowledge of the nature of universe and of man and the cultivation of political and intellectual virtues. Man has the ability, as a composite of immortal (soul) and mortal, to assimilate to God.

In On the issues that Aristotle diverges from Plato (De Differentiis) Pletho challenges the dominant notion of superiority of Aristotle and counters the Platonic thought as a more coherent and divine philosophy because it emphasizes the transcendent character of God creator.