Many things indeed are called universals among philosophers with some addition; as universal causes, universal signs, universal utterances, and those which in other modes so have unity that they nevertheless pertain to many. But the universal simply, and absolutely, and in no way singular, is defined to be that alone which, since it is some one thing, is apt by its nature to be in many; as animal in individual animals, and man in individual men. It is described also from a certain property: something one by nature apt to be predicated of many, or to be truly said. For since a thing is, or is not, a statement is called true or false. Thus animal is predicated of Alexander and Bucephalus, because it is perceived to be in them; and man similarly of Socrates, Plato, and Alcibiades, because it has its being in them.
It is not, however, necessary that what is universal be some one thing in reality in those of which it is predicated, as a road is said of that which is both ascending and descending at the same time in reality for those setting out from here and there; but in name and reason or concept. For as many things as there are in reality in which the universal exists, so many must that thing be in reality; in which manner we say animal in Alexander and Bucephalus to be two certain things, and man in Socrates, Plato, and Alcibiades three; yet not only the name, but also the reason of animal in Alexander and Bucephalus is one and the same; and in the same manner the name and reason of man in Socrates, Plato, and Alcibiades.
Nor indeed did philosophers say that whatever is universal is actually in many, but apt to be in many; because even if it is actually in only one singular, or even in none; if nevertheless it has the aptitude to be in many, whether simultaneously, as Orator or Prophet; or successively, as Monarch or Supreme Pontiff; it must by all means be reckoned universal.
Moreover the universal is said to be apt, not by external power, but by its own nature; because if something in the nature of things were such that by alien power it could not exist in many, to which, however, the nature of the thing considered would nothing repugn in being found in many; this part of its own nature and condition would be sufficient for it to be called universal. Although these two, which certain pagan philosophers, and certain others of ours in the World, and separate substances, thought to be true simultaneously, we judge to fight against each other.
Moreover it is not enough that some thing can be in many in any way, to be called universal by reason of their relation, as by real composition or inhesion; the latter definition shows this. For the soul is in man and horse as a real form in composite things; and whiteness in the swan and marble, as a real accident in inhesion in subjects: yet neither is this universal by comparison of the swan and marble; nor that with respect to man and horse, since they cannot be truly said of them: which same thing is easily observed in very many other things. But it is necessary that it be able to be in them by true identity, and such that those many affirm that thing to be in them.
Although neither is this enough, unless it is as it were their form: it will be, however, if it gives some being to them, either pertaining to their essence, or adjoined, or applied as it were to them as subjects. For which reason neither is body called universal by comparison of white and black; nor white or black with respect to sweet and soft, with which in butter white is conjoined, and black in cassia.
Finally, by the name of many, must be understood not any many, but such that in them that one thing is multiplied, and can be called many by its own name, as man in Socrates and Plato many men; and animal in man and horse many animals. For if something common is so in many, and is said of many, that nevertheless it is not multiplied in them, nor can many be called in them by its own name, that will no longer be said to be universal, but singular; in which manner the Best and Greatest God behaves in the comparison of divine persons.