in the subject possessing them, their view is false on several grounds, as has been explained at length elsewhere. Even supposing it to be correct, the middle term in thought has a wider scope than its counterpart in external reality, just as a proof has a wider scope than a cause. Every cause can be used to infer its effect, but not every proof is actually a cause. Likewise, whatever serves as an intermediary in reality can be made an intermediary in thought, thus serving as a proof, but the converse does not hold. For a proof is that which entails what it establishes. A cause that entails its effect can therefore be used to infer it. Similarly, a middle term that necessarily follows from what entails it, and itself entails a more remote consequence, entails that consequence and can therefore be used to infer it.

Thus, on any account, the desired conclusion can be established through a single premise if no other premise is needed. Sometimes, however, it can be established only through several premises, which must therefore be known. Insisting that exactly two premises are needed—neither more nor fewer—is entirely arbitrary. Hence, among all the various groups of rational people and authors in the sciences, you find no one who insists on demonstrating his arguments through two premises, no more and no fewer, striving to reduce any excess to two and to make up any shortfall so as to produce two premises, except the adherents of Greek logic and those who follow their path. This is not the practice of those who have retained their sound natural disposition or followed a path other than theirs, such as the Emigrants, the Helpers, those who followed them in righteousness, the other leading Muslim authorities, scholars and thinkers, and the various religious communities.

Likewise, among grammarians, physicians and geometers, none engages in this practice except those who follow these logicians in this respect, just as they followed them uncritically in adopting definitions composed of genus and differentia. They gained no knowledge from what they received from them except concerning matters for which their false discourse is unnecessary, or concerning what