The argumentative structures in Proclus’ Stoicheioseis

With his Elements of Theology the 5th century philosopher Proclus is the first to have written a metaphysical work “in the style of the geometers” (more geometrico). This means that it is presented as an ordered series of propositions, each of which is justified by one or more proofs, building exclusively on preceding propositions and/or common notions. Thereby he created an impressive model, conveying the impression of logical rigour, that would be very influential in the Middle Ages and for modern philosophy. This project compares this text with another work by Proclus also written in the style of the geometers, yet not in metaphysics but on the theory of motion: the Elements of Physics. We examine the argumentative structures in both works and study the way they implement Proclus’ ideas about the argumentative style used in manuals of geometry. We argue that both works are intended as exemplifying an axiomatic structure, which is chosen both for its justificatory power and for its didactic qualities, even though the texts do not always live up to those expectations. In other words, Proclus’ application of the axiomatic model is not perfect. We moreover study how Proclus, in other works, combines the axiomatic approach with another source of philosophical knowledge: exegesis of the authoritative texts of Plato. Finally we argue that Proclus’ use of the geometrical style was itself inspired also by book VI of Aristotle’s Physics, the earliest example of this method.