To us the religion of the Stoics is interesting chiefly as a part of the machinery by which they attempted to make good the connexion between natural and moral law, assumed rather than proved by their Sophistic and Cynic precursors. But before proceeding to this branch of the subject we must glance at their mode of conceiving another side of the fundamental relationship between man and the universe. This is logic in its widest sense, so understood as to include the theory of the process by which we get our knowledge and of the ultimate evidence on which it rests, no less than the theory of formal ratiocination. III. In their theory of cognition the Stoics chiefly followed Aristotle; only with them the doctrine of empiricism is enunciated so distinctly as to be placed beyond the reach of misinterpretation. The mind is at first a _tabula rasa_, and all our ideas are derived exclusively from the senses.[37] But while knowledge as a whole rests on sense, the validity of each particular sense-perception must be determined by an appeal to reason, in other words, to the totality of our acquired experience.[38] So also the first principles of reasoning are not to be postulated, with Aristotle, as immediately and unconditionally certain; they are to be assumed as hypothetically true and gradually tested by the consequences deducible from them.[39] Both principles well illustrate the synthetic method of the Stoics—their habit of bringing into close connexion whatever Aristotle had studiously held apart. And we must maintain, in opposition to the German critics, that their method marks a real advance on his. It ought at any rate to find more favour with the experiential school of modern science, with those who hold that the highest mathematical and physical laws are proved, not by the impossibility of conceiving their contradictories, but by their close agreement with all the facts accessible to our observation.