ALL the extant books attributed to Aristotle (including probably the recently recovered treatise on the Athenian Constitution) belong to the group of his works designated by ancient authorities ἀκροατικοì λóγοι, 'lecture-courses.' These are scientific treatises, in places hardly more than mere outlines, though for the larger part fully written out arguments; presumably they are records of Aristotle's doctrine made for his pupils, and preserved in the library of the Peripatetic School. The other class of his writings, now lost, were more popular expositions intended for the general reader; some of them were in dialogue form. They were published, and they are alluded to as νκδεδομèνοι λóγοι.
The former group includes three works on the philosophy of conduct, entitled the Eudemian Ethics, the Nicomachean Ethics and Magna Moralia. The two former are full scientific treatises, in eight and ten Books respectively. Magna Moralia is a smaller work, more discursive in style, of which only two Books survive, the latter part being lost; its contents correspond partly with the Eudemian and partly with the Nicomachean Ethics; it was probably compiled