But it is better to assume principles less in number and finite, as Empedocles makes them to be. All philosophers... make principles to be contraries... (for Parmenides makes principles to be hot and cold, and these he demominates fire and earth) as those who introduce as principles the rare and the dense. But Democritus makes the principles to be the solid and the void; of which the former, he says, has the relation of being, and the latter of non-being. ...it is necessary that principles should be neither produced from each other, nor from other things; and that from these all things should be generated. But these requisites are inherent in the first contraries: for, because they are first, they are not from other things; and because they are contraries, they are not from each other.
Aristotle