difference; for each of them possesses attributes that belong to him alone—attributes that may resemble those of another or differ from them. These attributes are individually instantiated; no one else shares in them in the least, although others may stand to them only in relations of similarity or dissimilarity. Now, when those individuated attributes(1) are considered in an abstract, universal way, the attributes that are alike constitute, for example, the species, whereas the attributes that are unlike constitute the genus. Thus likeness is exemplified by man with man and horse with horse, while unlikeness is exemplified by man with horse. The things that differ by the very essences of their kinds—humanity, for instance, in contrast to horseness—yet concur in the concomitant that follows upon those essences, namely the genus of animality. In every such case both the point of divergence and the point of agreement are absolute universals: neither of them is particular while the other universal, nor is one “one by person” and the other “one by genus,” as opposed to “one by person.” Rather, each individual man has a humanity that is unique to him together with an animality that is unique to him, just as every horse has its own horseness together with its own animality; it is like the various colors that all participate in the designation “colorness.”(2)
This thing is distinguished from that thing by the specificity of being white or black, for every determinate color has its own colorness and its own blackness or whiteness. If color is taken in the abstract and then divided into abstract whiteness and abstract blackness, neither abstract color nor abstract blackness nor abstract whiteness exists externally on condition of being abstract; it exists only in a determinate form. Once this whiteness and that whiteness are individuated, this color itself is individuated. Thus, the very entity that is called a genus, when instantiated in the external world, is the selfsame particular that externally belongs to the species: this color is precisely this blackness or this whiteness, and this animal is precisely this man and that horse.