Before he finishes the great chapter of which we have begun to speak he indicates that there are more ways than one of relating, or classifying, our facts; that, for instance, it may be equally proper and necessary to deal now with the animals and their several parts or properties, and at another time with the parts or properties as such, explaining and illustrating them in turn by the several animals which display or possess them. The 'Parts of Animals' is, then, a corollary, a necessary corollary, to the more anecdotal _Historia Animalium_. And yet again, there is a third alternative--to discuss the great functions or actions or potentialities of the organism, as it were first of all in the abstract, and then to correlate them with the parts which in this or that creature are provided and are 'designed' to effect them. This involves the conception and the writing of separate physiological treatises on such themes as Respiration, Locomotion, on Sleeping and Waking, and lastly (and in some respects the most ambitious, most erudite, and most astonishing of them all) the great account of the Generation of Animals. So the whole range, we might say the whole conceivable range, of biological science is sketched out, and the greater part of the great canvas is painted in. But to bring it into touch with human life, and to make good its claim to the high places of philosophy, we must go yet farther and study Life itself, and what men call the Soul. So grows the great conception. We begin with trivial anecdote, with the things that fisherman, huntsman, peasant know; the sciences of zoology, anatomy, physiology take shape before our very eyes; and by evening we sit humbly at the feet of the great teacher of Life itself, the historian of the Soul. It is not for us to attempt to show that even here the story does not end, but the highest chapters of philosophy begin. Then, when we remember that this short narrative of ours is but the faintest adumbration of one side only of the philosopher's many-sided task and enterprise, we begin to rise towards a comprehension of Roger Bacon's saying, that 'although Aristotle did not arrive at the end of knowledge, he set in order all parts of philosophy'. In the same spirit a modern critic declares: 'Il n'a seulement défini et constitué chacune des parties de la science; il en a de plus montré le lien et l'unité'. Aristotle, like Shakespeare, is full of old saws, tags of wisdom, jewels five words long. Here is such a one, good for teacher and pupil alike--Δει πιστευειν τον μανθανοντα {Dei pisteuein ton manthanonta}. It tells us that the road to Learning lies through Faith; and it means that to be a scholar one should have a heart as well as brains.