between its hypothetical parts imposes a unity upon it, yet it remains open to multiplicity because it can be divided, unlike the point.

The one by conjunction is that in which multiplicity exists in actuality: it is composed of different and dissimilar elements, but unity is nevertheless achieved through the linkage that binds those parts together. A single living animal, for example, is a compound of entities that differ in essence—skin, flesh, bone, and the like. Likewise, a single house is put together from walls, a roof, bricks, timber, and so forth. In such cases multiplicity is actual, not merely potential, whereas in a single line there is no actual multiplicity at all—only potential multiplicity. Here, then, multiplicity is actual because the parts are dissimilar, but the connection among them produces unity, so we say “this is one animal” or “one house” just as we say “one line” or “one surface,” though there is a difference between the two orders. In these three divisions the “one” is numerically and concretely one, even though the first of them, on close examination, has no existence outside the mind.

They also say: The one in genus is exemplified by the statement, “Man and horse are one,” because they share a single genus, namely animal.

The one in species is illustrated by the statement, “Zayd and ʿAmr are one,” for they belong to a single species, namely man.

The one by accident is like saying, “Ink and pitch are one,” that is, with respect to blackness, for blackness is an accidental attribute that inheres in both.

The one by relation is expressed in statements such as, “The relation of a king to his kingdom and the relation of the soul to the body are one,” or “the relation of a thing to a person’s very self, and the relation of…"