Chapters 9-10 (variants)

The term genus is used in three senses: in one sense, as coming from the progenitor, as those descended from Israel are called Israelites; in the second sense, as coming from the place of origin, as those from Jerusalem are called Hieroso-lymites and those from Palestine Palestinians; and, in the third sense, that is called genus which is divided into species. With this last the philosophers are concerned, and they define it by saying that genus is that which is predicated in respect to their common essence of several things which are specifically different.

The term species has two meanings. Thus, appearance and form are called species, as for example, the species of the statue. That is also called species which is subordinate to genus, that is to say, divided off from a genus. With this last the philosophers are concerned.

Now, when we are discussing genus, we mentioned species by saying that genus was that which was divided into species. Again, when discussing species, we mentioned genus by saying that species was that which was divided off from genus. One should know that when we discuss the father we must needs think of the son, too (for he is a father who has a son), and when we discuss the son we must needs think of a father, too (for he is a son who has a father). And similarly in this case it is impossible to treat of the genus without the species, or the species without the genus, for the genus is definitely divided into the species and that which does not have species divided off from itself is not genus. In the same way, the species are divided off from the genus and those things which do not have a genus are not species. And just as the first man—that is to say, Adam—is not called a son, because he had no father, but is called a father because he did have sons; and just as Seth is called both son of him that begot him, for he had Adam for his father, and father of him begotten by him, for he did beget a son; and just as Abel is called a son, because he had Adam for his father, but is not called a father, because he had no son— so also is it with genus and species.

The first genus, which is not divided off from a genus and has no higher genus, is genus only and not a species. This is called a most general genus and they define it by saying that a most general genus is that which, while it is a genus, is not a species with a genus higher than itself. Those things which are divided off from this, if they have other species lower than themselves and divided off from themselves, are at once species of those before them—that is to say, higher than themselves—from which they are divided off, and genera of those divided off from themselves —that is to say, of those which are lower than they. These are called subaltern genera and species. However, the species which are the last and the lowest and which do not have any lower species are not called genera but only species, because they have no lower species divided off from them.

For it is impossible to call that a genus which neither contains any species nor has any lower species divided off from itself. Therefore, the species which has no species is called a most specific species.

One should know that the species must admit of the name and definition of their genus and that the genus must admit of those of its genus up as far as the most general genus. The species, however, cannot admit of each other’s definition. Substance is a first and most general genus. For, even though substance and accident are divided from being, being is not their genus; and, although they do admit of the name of being, they do not admit of the definition. Being is defined as that which is either self-subsistent and without need of- any other for its existence, or that which cannot exist of itself but has its existence in another. Now, substance is a thing which is self-subsistent and without need of another for its existence, and it is that alone; accident is a thing which cannot exist in itself, but has its existence in another, and it is that alone. Thus, neither substance nor accident admits of the entire definition of being, but substance admits of one half and accident of the other. Species, however, will admit of both the name and the entire perfect definition of their genus. And so, even though being is divided into substance and accident, it is still not their genus. Nor, indeed, is substance a species with a genus higher than itself. On the contrary, it is a first and most general genus.

This substance, then, is divided into corporeal and incorporeal. Hence, the corporeal and the incorporeal are species of substance. Again, corporeal substance is divided into animate and inanimate. Here again the corporeal, while it is a species of substance, is the genus of the animate and the inanimate. Again, the animate is divided into sentient and non-sentient. Now the sentient is the animal, because it has both life and sensation; but the non-sentient is the plant, because it does not have sensation. The plant is called animate because it has the faculties of assimilating food, of growth, and of reproduction. Again, the animal is divided into rational and irrational. The rational is divided into mortal and immortal. The mortal is divided into rational man and the irrational animals such as the horse, the dog, and the like. None of these last is divided into any further species; they are divided into individuals, that is to say, individual substances. Thus, man is divided into Peter and Paul and John and all other individual men, who are not species, because 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. Man does not admit of the definition of the horse. But Peter and Paul and John do admit of one definition—that of man. And it is the same way with all other individual men. So, these last are not species of man. but they are individuals, that is to say, hypostases.

Again when the species is divided, it communicates both its name and its definition to those lower than itself. On the contrary, when Peter is divided into body and soul, he communicates neither his name nor his definition to the soul or the body, (For neither is the soul alone Peter, nor is the body; rather, he is both together.)

Still further, every division of genus into species will go as for as two or three, but very rarely to four species, because it is impossible for a genus to be divided into five or more species. But man is divided into all individual men, who 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. Neither is man the genus of Peter and all of the other individual men, but their species. For this reason man is a most specific species, because he is a species in relation to the higher and species in relation to the lower. Similarly, the horse, the dog, and the like are species and not genera, for which reason they are most specific species. Those coming in between the most general genus and the most specific species are subaltern genera. They are species of the higher and genera of the lower.

Then, there are also the essential and natural specific differences and qualities which are called dividing and constituent, because they divide the higher and are constituent of the lower. Thus, the corporeal and incorporeal substances divide substance. Similarly, the animate and inanimate divide the corporeal substance. Similarly, the sentient and non-sentient divide the animate. Ihese, then, go to make up the the animal, for I take an animate sentient substance and I have an animal, because the animal is an animate sentient substance. Then, 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. Then, again, 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, and the rational and the mortal and I have a man, for a man is a mortal rational animal. And I take the animal and the irrational and the mortal and I have the horse, say, or the dog, or the like. Now, differences are called essential and natural, because they make one species differ from another and one nature and essence differ from another essence and nature.

See alternate