History

Plato and Aristotle recognized that understanding nature demands reference to factors—what Aristotle called "final causes"—that in some sense anticipate what will or should happen. In the Timaeus, Plato wrote, "From the combination of sinew, skin, and bone, in the structure of the finger, there arises a triple compound, which, when dried up, takes the form of one hard skin partaking of all three natures, and was fabricated by these second causes, but designed by mind, which is the principle cause with an eye to the future." He continued, "For our creators well knew … that many animals would require the use of nails for many purposes; wherefore they fashioned in men at their first creation the rudiments of nails. For this purpose and for these reasons they caused skin, hair, and nails to grow at the extremities of...