Page:Greek Biology and Medicine.djvu/84

 GREEK BIOLOGY AND MEDICINE or rather discovering the paths of Nature's ordering. Thus he was a pioneer of natural science. But the intellectual needs of the philosopher drove him to another and more ultimate kind of pioneering. He must think the matter out, and find the logical, even the metaphysical basis of justification of his apprehension of Nature's processes: he must adjust his knowledge of Nature to the demands of his thought and possibly constrain it to the categories of his metaphysics." Let us follow him, for a little, here. Aristotle proceeds to attack the basic how and why of living things. His treatment of these organisms — that is, his biology — did not call for a discussion of the world's material, but merely its adaptability to nature's pur- poses. But his treatment did demand a dis- criminating conception of causation in order to understand how plants and animals came to be what they were. Although his analysis of the four kinds of causes is familiar, we may note the application made of it in his biology. " There are four causes underlying every- thing: first, the final cause, that for the sake of which a thing exists; secondly, the formal cause, the definition of its essence (and these [62]