Chapter 10

Species is also an equivocal term, since it is used in two different senses. Thus the form and appearance of anything is its species, as, for example, the species of the statue, in which sense it was once said: ‘a first species worthy of sovereignty.’ There is another kind of species, which is substantial and subaltern to genus. And again, species is that of which genus is predicated in the category of substance. Still again, species is that which is predicated in respect to their common essence of several things which are numerically different. The first two of these descriptions differ only relatively, like ‘ascent’ and ‘descent,’ and they apply to every species. The third and last description, however, applies only to the most specific species, which is that which is immediately above the individual and contains the individual substances—as we speak of the human species.

We have related how the term genus is used in three ways—genus from the progenitor and from the place of origin, each in two ways, and genus in a third way, in which the species is subaltern to it. The term species is used in two ways. In one way it is used for the form of anything. In the other way the genus is predicated of it and it is subaltern to genus, as being divided off from it. With this kind of genus and species the philosophers are concerned.

When we were discussing genus, we mentioned species, when we said that genus was that which was divided into species. And again, when discussing species, we mentioned genus by saying that species was that which was divided off from genus. Thus, one should know that when we speak of a father we must needs think of the son, too (for he is a father who has a son), and when we discuss a son we must needs think of the father, too (for he is a son who has a father). And similarly, in this case, it is impossible to discuss genus without species or species without genus, for genus is definitely divided into species and that which does not have species divided off from it is not genus. In the same way, the species are divided off from a genus and those things which do not have a genus are not species.

Now, just as the first man—namely, Adam—is not called a son, because he had no father, but is called a father because he did have sons; and as Seth is both called the son of him who begot him, because he did have Adam for his father, and is also called the father of the one begotten by him, because he did beget Henoch; and as Abel is called a son, because he had Adam for father, but is not called a father, because he had no son—just as with these, so also it is with genus and species. The first genus, since it is divided off from no other genus and has no genus higher than itself, is genus oniy and not species. This is called the most general genus and we define it by saying that a most general genus is that which, while it is a genus, is not a species, because it has no genus higher than itself. Those things which are divided off from this, if they have other species inferior to themselves and divided from them, are at once species of those prior to them—that is to say, superior to themselves—-from which they themselves have been divided off, and genera of those things divided off from them, which is to say, of those inferior to themselves. These are called subaltern genera and species. But the species which are the last and the lowest and which do not possess any lower species, that is, do not contain any species but just individuals—that is to say, individual substances—these are not called genera but just species, because of their not having, as I have said, any lower species divided off from themselves.

For it is impossible to call that a genus which neither contains any species nor has any lower species divided off from it. Therefore, that which does not contain any species, but only individual substances, is a most specific species, because, although it is a species, it nevertheless is not a genus. Similarly, the genus which is not a species is called a most general genus.

One should know furthermore that the species necessarily admit of both the name and the definition of their genus, and the genera of their genera up as far as the most general genus. The species, however, cannot admit of each others definition. Now, to make the matter under discussion clearer, let us look at it in the following manner. Substance is the first and most general genus, for, although substance as well as accident is divided from being, being is not their genus. This is because, although they both admit of the name of being, they do not admit of its definition. A being is a thing which is either self-subsistent and without need of any other for its existence or which cannot exist of itself but has its existence in another. But, substance is a self-subsistent thing and has no need of another for its existence, and that is all. Thus, substance does not admit of the entire definition of being. Consequently, being is not the genus of substance, nor is substance [a species] of being, for the species admits of the definition of its genus in its entirety. What is more, accident is not a species of being either—because it does not admit of its entire definition, but only of half of it. This is because an accident is a thing which cannot exist of itself, but only has its existence in another. Thus, neither substance nor accident admit of the entire definition of being, but substance admits of one half and accident of the other. And so, even though being is divided into substance and accident, it is not their genus. Substance, however, is divided into corporeal and incorporeal substance. Here, the corporeal and the incorporeal are species of substance, because each of them admits of the name and the definition of substance. Thus, substance is not a species, because it has no genus higher than itself; rather, it is a first and most general genus. And again, the corporeal substance is divided into animate and inanimate. Here again, while the corporeal substance is a species of substance, it is the genus of the animate and inanimate. The animate is further divided into sentient and non-sentient. Now, the animal is sentient, because it has life and sensation; whereas the plant is non-sentient, because it does not have sensation. The plant, however, is called animate because it has faculties of assimilating food, of growing, and of reproducing. Again, the animal is divided into rational and irrational. The rational is divided into mortal and immortal, and the mortal into man, the horse, the ox, and the like, which admit no further division into other species, but only into individuals, that is to say, into individual substances. Thus, man is divided into Peter, Paul, John, and all other individual men, who are not species but hypostases. For the species, as we have said, do not admit of each other’s definition. For example, the corporeal substance does not admit of the definition of the incorporeal, nor does man admit of the definition of the horse. Peter and Paul and John, however, do admit of one definition: that of man. It is the same for all other individual men; hence there are not various species of men, but individuals, that is to say, hypostases.

Again, when the species is divided, it communicates both its name and its definition to those inferior to itself. However, when Peter is divided into body and soul, he does not communicate his name and his definitions either to the soul or to the body. For Peter is not the soul alone or the body alone but both of them together.

Still further, every division of genus into species will go as far as two or three or, very rarely, four species, because it is impossible for a genus to be divided into five or more species. Man, on the other hand, is divided into all individual men, and these are unlimited in number. For this reason there are some who say that that which is from species to individuals is not to be called division, but enumeration. Whence it is clear that Peter and Paul and John are not species but individuals, that is to say, hypostases. Nor is man the genus of Peter and Paul and John and the other individual men, but their species. Thus, man, too, is a most specific species, for he is a species belonging to the superior order in so far as he is contained under it; and he is the species of those inferior to himself, in so far as containing them. For, that which is contained by a genus is a species, and that which contains the individuals, or individual substances, is also species. This last, then, is the most specific species, which comes immediately above the individuals, and which they define by saying that it is a species which is predicated in the category of essence of several numerically different things. In the same way, the horse and the dog and other such species are most specific. Those which stand between the most general genus and the most specific species are subaltern genera and species—species of the superior order and genera of the inferior.

Then there are also the essential and natural differences and qualities which are called dividing and constituent, because they divide the superior and constitute the inferior. Thus, the corporeal and incorporeal divide substance. Similarly, the animate and the inanimate divide the body. Similarly, the sentient and the non-sentient divide the animate. These, then, go to make up the animal, for I take an animate sentient substance and I have an animal, because the animal is an animate sentient substance. Again, I take an inanimate non-sentient substance and I have a stone. Again, I take an animate non-sentient substance and I have a plant. Further still, the rational and the irrational divide the animal, and the mortal and the immortal divide the rational. So I take the animal, which is the genus of these last, and the rational and the mortal and I have a man, for man is a mortal rational animal. Then I take the animal and the irrational and the mortal and the terrestrial and I have a horse, a dog, and the like. Or I take the irrational and the mortal and the aquatic and I have a fish. Now, differences are called essential and natural, because they make one species differ from another and one nature and essence from another essence and nature.

See alternate