 We should also make selections from the literature and include these in separate lists for each set, with separate headings, for instance ‘On the Good’, or ‘On the Living Being’—that is to say the Good as a whole, starting with (the question) ‘what is it?’ One should cite the doxai [opinions, tenets] of individual thinkers, e.g., that Empedocles said that the elements of bodies are four in number […].