 Fârâbî gives two arguments that, if X is first, it cannot have a contrary Y. Both arguments turn on a definition of “contrary”: X and Y are contrary if they cannot be together in the same place or substratum, so that X is present in some place or substratum through Y’s being absent from it, and X is absent from a place or substratum through Y’s being present in it. On the basis of this definition, Farâbî argues, first, that if the First, X, were contrary to Y, then X’s being (in some place or substratum, or being at all) would be conditioned on Y’s absence, and therefore X’s substance would not be sufficient to explain X’s continuing to exist, or X’s existing at all: so, Fârâbî says, X’s constitution [qiwâm] would not be in X’s substance (alone), but would be through something else, and so X would not be first. Second, X and Y would have to have something common that is receptive of both of them, so that this common thing would persist in being and X and Y would succeed each other in it, and so this common thing would be prior to them and neither of them would be first. These arguments are recognizably developments of Aristotle’s arguments in Metaphysics XII against there being a pair of contrary first principles like Empedocles’ Love and Strife, although Aristotle relies on the premiss that the first principle is pure actuality, while Fârâbî makes relatively little use of the notion of actuality and relies on the premisses that the first principle is simple and that it does not depend on anything else for its  existence.[51]  Fârâbî’s conclusion that the First has no contrary is not simply a special case of his conclusion that the First has no partner, or as he says that “nothing other than it can have the existence [wujûd] that it has”, since he does not assume that contraries would have the same existence or would be members of the same species or genus.