De ente et essentia

Having seen, then, what is signified by the name essence in composite substances, we must consider how it is related to the notion of genus, species, and difference. Since, moreover, that to which the notion of genus, species, or difference belongs is predicated of the designated singular, it is impossible that the notion of universal—namely, of genus or species—belong to the essence insofar as it is signified in the manner of a part, as by the name humanity or animality. Hence Avicenna says that rationality is not a difference but the principle of a difference; and for the same reason humanity is not a species, nor animality a genus.

Likewise, it cannot be said that the notion of genus or species belongs to the essence insofar as it is some existing thing outside singulars, as the Platonists posited. For in that case genus and species would not be predicated of this individual: one could not say that Socrates is that which is separated from him; nor would that separated thing contribute to knowledge of this singular. It therefore remains that the notion of genus or species belongs to the essence insofar as it is signified in the manner of a whole, as by the name man or animal, insofar as it implicitly and indistinctly contains the whole of what is in the individual.

Nature or essence, so understood, can be considered in two ways. In one way, according to its proper notion; this is its absolute consideration. In this way nothing is true of it except what belongs to it as such; hence whatever else is attributed to it is a false attribution. For example, rational and animal, and other things that enter into the definition of man, belong to man insofar as he is man; but white or black, or anything of this sort that does not belong to the notion of humanity, does not belong to man insofar as he is man. Thus, if it is asked whether this nature, so considered, can be called one or many, neither may be granted, because both are outside the understanding of humanity, and either can befall it. For if plurality belonged to its understanding, it could never be one, although it is one insofar as it is in Socrates. Likewise, if unity belonged to its notion, then it would be one and the same in Socrates and Plato, and could not be multiplied in many.

In another way, it is considered according to the being that it has in this or that; and in this way something is predicated of it accidentally, by reason of that in which it is, as when it is said that man is white because Socrates is white, although this does not belong to man insofar as he is man.

This nature has a twofold being: one in singulars and another in the soul; and according to each, accidents follow upon the nature in question. In singulars, too, it has multiple being according to the diversity of singulars. Yet none of these kinds of being is owed to the nature itself according to its first consideration, namely, the absolute one. For it is false to say that the essence of man, insofar as it is such, has being in this singular; for if being in this singular belonged to man insofar as he is man, he would never be outside this singular. Likewise, if not being in this singular belonged to man insofar as he is man, he would never be in it. But it is true to say that man, not insofar as he is man, has it that he is in this singular or that one, or in the soul. Therefore it is clear that the nature of man, absolutely considered, abstracts from every being, yet without making a precision of any of them. And this nature, so considered, is what is predicated of all individuals.

Nevertheless, it cannot be said that the notion of universal belongs to nature so accepted, because unity and commonality belong to the notion of universal; neither of these, however, belongs to human nature according to its absolute consideration. For if commonality belonged to the understanding of man, then wherever humanity were found, commonality would be found; and this is false, because no commonality is found in Socrates, but everything that is in him is individuated. Likewise, it cannot be said that the notion of genus or species befalls human nature according to the being it has in individuals, because in individuals human nature is not found according to unity, so as to be one thing belonging to all, which the notion of universal requires. It therefore remains that the notion of species befalls human nature according to the being it has in the intellect. Indeed, human nature itself has in the intellect a being abstracted from all individuating features; and therefore it has a uniform relation to all the individuals outside the soul, insofar as it is equally the likeness of all and leads to knowledge of all insofar as they are men. From the fact that it has such a relation to all individuals, the intellect devises the notion of species and attributes it to the nature. Hence the Commentator says at the beginning of On the Soul that “the intellect is what produces universality in things”; Avicenna says this too in his Metaphysics.

Although this understood nature has the notion of universal insofar as it is compared with things outside the soul, because it is one likeness of all, nevertheless, insofar as it has being in this intellect or that one, it is a particular understood species. Hence the Commentator’s error is clear in Book III of On the Soul, where he wished to conclude the unity of the intellect in all men from the universality of the understood form. For that form is not universal insofar as it has this being in the intellect, but insofar as it is related to things as their likeness; just as, if there were one corporeal statue representing many men, it is clear that the image or species of the statue would have singular and proper being insofar as it were in this matter, but would have the notion of commonality insofar as it were a common representation of several.

And because it belongs to human nature according to its absolute consideration that it be predicated of Socrates, while the notion of species does not belong to it according to its absolute consideration but is among the accidents that follow upon it according to the being it has in the intellect, the name species is not predicated of Socrates, so that one would say “Socrates is a species.” This would necessarily follow if the notion of species belonged to man according to the being he has in Socrates, or according to his absolute consideration, namely, insofar as he is man; for whatever belongs to man insofar as he is man is predicated of Socrates.

And yet, since being predicated belongs to genus per se, it is posited in its definition. For predication is something completed through the action of the intellect composing and dividing, having in the thing itself a foundation, namely, the unity of those things one of which is said of the other. Hence the notion of predicability can be included in the notion of this intention, which is genus, and which likewise is completed through an act of the intellect. Nevertheless, that to which the intellect attributes the intention of predicability, composing it with another, is not the intention of genus itself, but rather that to which the intellect attributes the intention of genus, such as what is signified by the name animal.

Thus it is clear how essence or nature is related to the notion of species: the notion of species is not among those things that belong to it according to its absolute consideration, nor is it among the accidents that follow upon it according to the being it has outside the soul, such as whiteness and blackness; rather, it is among the accidents that follow upon it according to the being it has in the intellect. In this way, the notion of genus or difference also belongs to it.