Section

Now that this has been clarified, we say: The answer to this proof—which is the very foundation of their discourse and which the questioner has carefully set down and greatly expanded, drawing it from Avicenna’s al-Ishārāt, with Fakhr al-Rāzī and others providing commentaries—is that we shall expose the unsoundness of everything they have asserted in each of the four categories from several angles. Indeed, refuting a single category by a single argument would suffice to invalidate the whole, for a proof is not complete unless every one of its alleged entailments stands. If even one of those entailments could be shown to hold once its necessity is established, their claim would collapse. We shall therefore demonstrate the flaw both in what they regard as the consequents and in what they regard as the antecedents, so that the falsity of both premises—the conditional and the disjunctive—becomes evident. This will be done in several ways.

First: One poses to him the question, “What is your initial evidence for restricting the matter to these four categories? A logically exhaustive division requires us to say: either it is a consequent, an antecedent, an attribute, a substratum, or it is none of these—neither consequent nor antecedent nor attribute nor substratum. The intellect can certainly conceive this fifth possibility. You are not entitled to claim that its non-existence is self-evident, for ordinary intellects do not perceive its impossibility as an intuitive certainty. And even if its impossibility could be known by rational inquiry, the burden still falls on you to prove it before the argument can be considered complete.”

If he then says, “Whenever two things coincide, their relationship must belong to one of these four categories,” the reply is that if by ‘coincide’ you mean coexistence in external reality, or coexistence in