To the Greek, attempting to give a scientific account of motion, the purely mechanical view hardly suggested itself, except in the case of a few men of genius such as Democritus and Archimedes. Two sets of phenomena seemed important: the movements of animals, and the movements of the heavenly bodies. … To the Greek, it seemed more natural to assimilate apparently lifeless motions to those of animals. A child still distinguishes live animals from other things by the fact that they can move of themselves; to many Greeks, and especially to Aristotle, this peculiarity suggested itself as the basis of a general theory of physics.

Bertrand Russell, History of Western Philosop…, loc. 866