…in external reality, for among concomitants there is no order that would make some of them first and others second; nor is there such an order in the mind, for the “middle term” is nothing but the proof itself. The distinction therefore collapses into the simple rule that first principles (awwaliyyāt) are those that need no proof, whereas theoretical propositions are those that do. This is a sound and universally accepted statement that has no need of the elaborations they have offered. Yet it follows that whether a given proposition is primary or theoretical is purely relative: what is self-evident to Zayd may be theoretical to ʿAmr, depending on how fully each has conceived the matter. Whenever a person’s conception of a thing is more complete than another’s, he will perceive some of its concomitants that the one with the deficient conception does not perceive; he therefore needs no middle term to know those concomitants, while the other does. Moreover, none of this implies that widely accepted propositions (mashhūrāt) are any less certain, as we shall explain, God willing.

Avicenna’s rejoinder to their distinction between essential attributes and concomitants:

Avicenna says verbatim in his Ishārāt:

“Now the non-constitutive concomitant is specifically called a ‘concomitant’. If what is constitutive is also a concomitant, it is that which accompanies the quiddity without being a part of it—such as the fact that a triangle’s angles equal two right angles.

If the entailment of such a concomitant is without a middle term, its necessity is known and it cannot even be imagined away, despite its not being constitutive. But if it does have a clarifying middle term, then through that middle term its necessity is understood.

By ‘middle term’ I mean whatever we attach to our statement when we say, ‘because it is such-and-such’. If this middle term is constitutive of the thing, the concomitant itself is not constitutive of it—for the constituent of a constituent is itself a constituent—but is rather another concomitant. Should that in turn require a middle term, the process would regress without end and the term would not be a true middle. If it does not require a middle term, then we have before us a concomitant whose entailment is without a middle term.

Likewise, if the middle term is an antecedent concomitant that itself needs the mediation of yet another concomitant or constituent until one reaches a concomitant entailed without a middle term, the series would again regress ad infinitum. Therefore, in every case it is necessary that…”