This study investigates the idea of harmony as a protological and eschatological principle in three outstanding Patristic philosophers, well steeped in the Platonic tradition: Origen, Gregory Nyssen, and Evagrius. All of them attached an extraordinary importance to harmony, homonoia, and unity in the arkhē and, even more, in the telos. This ideal is opposed to the disagreement/dispersion of rational creatures’ acts of volition after their fall and before the eventual apokatastasis. These Christian Platonists are among the strongest supporters of the (...) final universal restoration. Their reflection on the unity-multiplicity dialectic, which parallels that between harmony and disorder/discord/dissonance, is informed by the Platonic tradition. In Gregory, the idea of harmony assumes musical connotations, especially in relation to the telos. In this connection, I examine the relationship between their notion of harmony in the arkhē and telos and Plotinus’ concept of harmony. Plotinus was well known to Gregory, the author of a Christianized version of Plato’s Phaedo in which apokatastasis is prominent. Origen, whose readings included many Middle-Platonic and Neo-Pythagorean texts, in Alexandria attended the classes of the “proto-Neoplatonist” Ammonius, who was also Plotinus’ teacher. A wide-ranging methodical investigation of the relation between Origen’s and Plotinus’ philosophical thoughts is still a notable desideratum. Finally, I concentrate on the concept of harmony in astronomy as a metaphor for intellectual harmony and apokatastasis in Patristic Platonism, especially in Evagrius’ Kephalaia Gnōstika. The noun apokatastasis was used in an astronomical sense, and employed in Stoicism for the conclusion of a cosmic cycle. Evagrius, who loved astronomical metaphors, focussed a kephalaion on a wordplay—which escaped Guillaumont and all other scholars—concerning the astronomical meaning of apokatastasis, thus embedding his theory of the eventual restoration in an allegorical framework that rests on a notion of astronomical harmony. A strong case is made in this connection that Evagrius was elaborating on Plato’s pivotal link between cosmological and intellectual harmony, and was aware that the Stoic theory of cosmological apokatastasis drew on Plato. (shrink)