Definition in Ancient Philosophy is a theme at the crossroads of metaphysics and epistemology, with wider implications, for example in the philosophy of language and the philosophy of science. While the question of what constitutes a good definition is already addressed in Plato, in relation with the ti esti question, definitions runs across the whole spectrum of Ancient Philosophy.

The Ancient Philosophy research group studies definition in Antiquity. In November 2023, the conference "Definition between Plato and Aristotle", co-organised with David Meißner (Bonn), was held in Freiburg as part of the Theoretical Philosophy Working Group of the Society for Ancient Philosophy (Ganph).

In June 2024, we will hold our first international summer school on the topic of 'Definition, Essence and Explanation in Ancient Philosophy' from 10 to 15 June, with Katja Vogt (Columbia) and Pieter Sjoerd Hasper (Hamburg) (information to follow).