One key way in which the prima via can be misunderstood happens when one looks at it as a prescription for a mechanistic universe. A moves because it is pushed by B. B, being a bodily being, moves A only because it is moved by C. D is related to C as C was to B, etc. This series cannot be infinite, therefore there must be a non-pushed pusher. But Aristotle's cosmology is full of things that act, not because they are pushed, but because they desire to act as they do, or something analogous thereto occurs in them. Animals are the perfect example, because there desire in the proper sense does occur (craving would be a better word, come to think of it: desire is more proper to humans, but that's beside the point). They are the source of their own motion in a way that is far different from how a rock falls when you let it go. When animals act in a distinctively animalian mode, they determine how they shall act on the basis of forms that the...
Commentary and discussion regarding science, faith and culture by Leo White