Introducing his commentary on Ptol. Harm. I.5, Porphyry discusses at length the vocabulary of musical intervals and in particular the question whether the words λόγος and διάστηµα should or not be used as synonyms. This paper aims, on the one hand, at analysing the way in which he chooses and arranges his sources; on the other hand, at restoring them to the original debate to which they belong—a debate in which a seminal role seems to have been played by Plato’s Timaeus and the contributions of its early commentators (Eratosthenes, Aelianus, Panaetius) in the framework of post-Aristoxenian harmonics.
This contribution is meant to shed light on how ancient Greek music theorists structure argumentations and address their readership in order to be understandable, effective and persuasive. On the one hand, some of the most important treatises, e.g. Ptolemy’s Harmonics (with Porphyry’s Commentary) and what remains of Archytas’ and Theophrastus’ works, are taken as case studies; on the other hand, the paper deals with some argumentative patterns recurring in harmonics demonstrations, especially with reference to the usage of everyday life experience as evidence supporting acoustic and harmonic theories.