From the 1st century BC onwards followers of Plato began to systematize Plato's thought. These attempts went in various directions and were subjected to all kinds of philosophical influences, especially Aristotelian, Stoic, and Pythagorean. The result was a broad variety of Platonisms without orthodoxy. That would only change with Plotinus. This volume, being the fruit of the collaboration among leading scholars in the field, addresses a number of aspects of this period of system building with substantial contributions on Antiochus and Alcinous and their relation to Stoicism; on Pythagoreanising tendencies in Platonism; on Eudorus and the tradition of commentaries on Aristotle's Categories; on the creationism of the Jewish Platonist Philo of Alexandria; on Ammonius, the Egyptian teacher of Plutarch; on Plutarch's discussion of Socrates' guardian spirit. The contributions are in English, French, Italian and German.