1. Tusculan Disputations, V. 4. 10; cf. Aristotle, Metaphysics 987b1 ff. and Pans of Animals 642024 ff. See Xenophon, Memorabilia I. 1 and IV. 7, and Plato, Phaedo 96a ff. and Apology 19b-d, for Socrates’ views on the various sciences.