Sextus Empiricus Pyrrhoniae Hypotyposes 2.2.13

[13] The Stoics, then, and several others, ¹ say that there are three divisions of philosophy, namely, Logic, Physics, and Ethics; and they begin their teaching with Logic, ² although the question of the right starting-point is also a matter of much controversy. So we shall follow them in an undogmatic way; and since the subject matter of all three divisions requires testing and a criterion, and the doctrine of the criterion seems to be included in the division of Logic, we shall begin with the doctrine of the criterion and the division of Logic.