Book 7
1.40
Philosophy, they say, is like an animal, Logic corresponding to the bones and sinews, Ethics to the fleshy parts, Physics to the soul. Another simile they use is that of an egg: the shell is Logic, next comes the white, Ethics, and the yolk in the centre is Physics. Or, again, they liken Philosophy to a fertile field: Logic being the encircling fence, Ethics the crop, Physics the soil or the trees. Or, again, to a city strongly walled and governed by reason.
1.40
No single part, some Stoics declare, is independent of any other part, but all blend together. Nor was it usual to teach them separately. Others, however, start their course with Logic, go on to Physics, and finish with Ethics; and among those who so do are Zeno in his treatise On Exposition, Chrysippus, Archedemus and Eudromus.