Now our foregoing discourse, save for a few matters, has set forth the works wrought by the craftsmanship of reason; but we must now set beside them the things that come about of necessity. For the generation of this universe was a mixed result of the combination of necessity and reason. Reason overruled necessity by persuading her to guide the greatest part of the things that become towards what is best; in that way and on that principle this universe was fashioned in the beginning by the victory of reasonable persuasion over necessity. If, then, we are really to tell how it came into being on this principle, we must bring in also the wandering cause – in what manner its nature is to cause motion. So we must return upon our steps thus, and taking, in its turn, a second principle concerned in the origin of these same things, start once more upon our present theme from the beginning, as we did upon the theme of our earlier discourse.