Physics

and exist and come to be; it is better to take fewer and finite ones, which is what Empedocles does.

Indeed, all men make the opposites their principles: those who say that the whole is one and unmoved (for even Parmenides makes hot and cold principles, and designates these as fire and earth), and those who make them rare and dense, and Democritus the solid and the void, the one of which he calls existing and the other non-existing; furthermore, by position, by shape, by order. These are genera of opposites: of position, above-below, before-behind; of shape, angular-straight-curved. That everyone in some way makes the opposites their principles is clear. And this is reasonable: for principles must neither be from each other nor from others, and all things must be from them. The first opposites possess these traits, because as first principles they are not from others, and because as opposites they are not from each other. But this must also be examined through argument to see how it follows. We must first accept that of all existing things, nothing is naturally suited to act upon or be acted upon by just anything, nor can just anything come to be from just anything, unless one takes it as being by accident. For how could white come to be from musical, unless the musical happened to be an accident of the non-white or the black? But white comes to be from non-white, and not from any non-white, but from black or something intermediate; and musical comes to be from non-musical, not from any non-musical, but from unmusical or something intermediate between them. Nor does it perish into just anything, for example, white does not perish into musical, unless perhaps by accident, but into non-white, and not into just anything, but into black or something intermediate. Likewise also, musical perishes into non-musical, and this not into just anything, but into unmusical or something intermediate. And this is the same for other things, since even things that are not simple but composite follow the same rule. However, because the opposing states have not been named, this occurrence escapes notice.