Miguel De Beistegui corollates the principle of identity with the principle of contradiction, from "Onto-tauto-logy".

If difference can lead as far as contrariety [Metaphysics, Ι, 4], it cannot lead as far as contradiction. To the extent that difference is thought on the basis of a prior identity, contrariety constitutes its absolute limit. The principle of contradiction is quite naturally the corollary of the principle of identity, so long as difference is thought on the basis of the latter. And it comes as no surprise, then, that this principle should have had such a destiny, perhaps expressed nowhere more strongly than by Leibniz. The principle of identity (A=A) claims that a concept or a thing, in order for it to be the concept or the thing that it is, must remain identical to itself. By contrast, the principle of contradiction claims that whatever includes a contradiction can be neither true nor real. Indeed, since the principle of identity presupposes a definition of truth and reality through self-identity or self-coincidence, whatever includes a contradiction does not coincide with itself, and is thus, at the level of cognitions, false, and at the level of realities, unreal. Only that which has the form of self-identity is "real" or "true."

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