  William offers a host of arguments against the possibility of two first principles. On metaphysical grounds, for example, he objects that a first principle must be a being necessary through itself, and that he has shown that a plurality of such beings is impossible. And he gives arguments to the effect that the notion of a creative first evil principle is incoherent. Such a being, for example, could not do good for anything, and hence could not have created anything, for in doing so it would have done good for what it created.