They further maintain that numerality is not a common essential attribute of the even and the odd, and that evenness and oddness are not distinguishing essentials of the even number and the odd. With respect to colorness, they sometimes treat it in the same way as animality and declare it essential, while at other times they liken it to numerality and pronounce it non-essential. Their justification is that a given number’s being even or odd may be concealed and therefore cannot be known except by means of an intermediary proof, whereas the fact that a human being, a horse, a camel, a donkey, an ape, and the like are animals is obvious to everyone.

It is well known, however, that every necessary attribute is either peculiar to the subject—so that it may serve as a differentia—or shared with something else; yet in external reality both kinds remain one with the subject itself. Just as blackness is the colour, an accident inhering in something else, and three is the number, which is the odd, so man is the animal that is rational, and the horse is the animal that neighs; and so it goes with all other things that are defined.

Their assertion that the concept they designate as “essential” is formed in the mind prior to the conception of the thing itself, whereas the other attribute is not, is invalid for two reasons.

First, this claim merely reports their own mental convention: they choose to place one idea first in their minds and postpone the other, and this is sheer arbitrariness. Anyone who gives precedence to one attribute over another is simply copying them. It is evident that external realities, which exist independently of us, are not subordinate to our conceptions; rather, our conceptions follow them. Thus, imagining one attribute to be prior and another posterior does not make it so outside the mind. The rest of humanity, who have not adopted their convention, do not perceive this ordering at all. Were it truly innate, the natural disposition (fiṭrah) would grasp it without recourse to the convention that distorts it, just as it apprehends other innate matters. What the fiṭrah recognises is only that all these concomitants belong to the subject: they may occur to the mind or they may not; and whenever they do, a person’s knowledge of the subject increases, whereas when they do not, his knowledge of its attributes is diminished. But to claim that one of these attributes lies outside the essence while another lies within it—this