This sound, in turn, is either essential (ousiwdhs) or applied to the essence (epousiwdhs). Essential is that sound which expresses the substance or nature of things; and that which is applied to the essence is that which expresses accidents. For example: man is a mortal rational animal. All these will be significant sounds. For if you take any of these things away from a man, he will not be a man. And if you say that he is not an animal, then he is no longer a man; and if you say that he is not intelligent, then he is no longer a man; in the same way, if you say that he is not mortal, he is not a man; for every man is an animal, and rational, and mortal. Therefore (these sounds) are called essential because they complete the nature of man, and it is impossible for man to exist outside of them. In like manner, in every thing, that which constitutes its nature is called essential; and what is applied to the essence are accidents, which may or may not be in the subject, such as a man or a horse, or something else like that, for example, white. For whether a man be white or black, he will nevertheless remain a man. This and the like are called those which are applied to the essence, or accidents, which we may have either these or their opposites.

Essential sound denotes either what a thing is or what this thing is. For example, answering the question of what a human being is, we say: animal. Then, asked what kind of animal, we say: rational, mortal. The essential sound that shows what an object is is called difference (diafora); but he who shows what an object is designates either many species and constitutes a genus, or many individuals differing from each other in number, but in no case in species, and constitutes a species. The first, i.e., the genus, is, for example, substance, for substance signifies man, horse, and ox, because each of these beings is called and is substance, but the one is one species, the other another. The second, i.e., species, is, for example, man, for this word signifies many, or rather all individuals, who differ from each other in number, for the one is Peter and the other is Paul, and they are not one, but two, but in kind, that is, in nature, they do not differ. In fact, they are all called and are people.

Thus there is the most particular [individual, as opposed to genus and species], differing from each other in number, e.g., Peter, the individual, and also the person and hypostasis (prosopon kai upostasis). It denotes someone definite. Thus, when we are asked; "Who is this (man)," we say, "Peter." This is also indicated by the expressions "other" — for one is Peter and the other — Paul — "he," "this," "that"—they are applied to the individual who exists in himself, and the like. This word embraces Peter, Paul, and all individual people. The Holy Fathers call the species nature (fusis) and essence (ousia) and form (morfh). That which embraces a multitude of species is called a genus, e.g., "animal," because it embraces man, ox, horse, and is more general than a species. The Holy Fathers call both species and genus nature, form, image, essence. Through the species, that is to say, nature, essence, form, it is not this or that individual, not this or that difference, but this or that substance that is posited. Thus we call man one entity, the horse another, but not one or another individual. As for the species, it is said: this, it, that, and the like, i.e., that which answers the question: "What is an object?" As for what is applied to the essence, it belongs either to one species or to many. If it belongs to one species, it is called a property; For example, the ability to laugh, which belongs to one person, the ability to neigh, which belongs to one horse. If it belongs to many species, it is an accident, for example, whiteness, for it belongs to man, and to horses, and dogs, and many other species. Such are the five names to which every philosophical name is reducible, and we need to know what each of them signifies, and in what ways they resemble each other, and in what they differ. These names are: genus, species, difference, property, and accident.

A genus is that which is expressed, i.e., said and named, in relation to many objects differing from each other in kind, to the question: What is an object? For to speak is to be said about something.

A species is that which is expressed in relation to many objects differing from each other in number, to the question: What is an object?

Difference is that which is said in relation to many objects that differ from each other in kind, to the question: What is the object? and is accepted in the definition as an essential feature. The difference cannot be and not be in one and the same form, but must necessarily be in the form to which it belongs. Being present in it, it preserves it: in its absence, it destroys it. In the same way, it is impossible that both difference and its opposite should be combined in one form. For example, rationality cannot but belong to man, for an irrational being is no longer a man. Being present, rationality constitutes the nature of man, and when absent, it destroys, for an irrational being is no longer a man. It should be noted that difference is called essential, natural (fusikh), component (sustatikh), dividing, as well as specific difference, essential quality and natural property of nature. Philosophers very aptly call it difference, since it is the most special and is the expression of the essence to which it belongs.

A property is that which belongs to one species, to all things, and is capable of being addressed, such as the ability to laugh. In fact, every man is capable of laughing, and every creature capable of laughing is a man.

Accident is that which is said about many objects that differ in kind, to the question: What is the object? It is not accepted in the definition, but it can both belong to the object and not belong to it. An accident, being present in an object, does not preserve it and, being absent, does not destroy it. Accident is called non-essential (epousiwdhs) difference and quality. Accident can be either separable or inseparable. A separable accident is that which is now present and sometimes absent in one and the same person, such as sitting, flying, standing, sickness, health. An inseparable accident is that which does not enter into the composition of the essence, because it is not contemplated in its entirety, but since it belongs to a certain person, it can no longer be separated from him. Such, for example, is the flattening or humpback of the nose, the blue of the eye, etc. Such an inseparable accident is called a distinguishing feature (carakterikon idioma), because this difference constitutes the hypostasis, i.e., the individual.

As for the individual, he is composed of substance and accidents, and exists by himself, differing from his peers in appearance, and showing not "what," but "whom." But with God's help, we will become more thoroughly acquainted with this later.

Chapter VI: On Division. Division is the first division of a thing; For example, an animal is divided into rational and irrational. An additional division (epidiaireosis) is a second division of the same thing. For example, an animal is additionally divided into legless, bipedal, and quadruped: legless — fish, bipedal — man and bird, quadruped — ox, horse, and the like. Subdivision is the dismemberment of the separated part. For example, an animal is divided into rational and irrational, while rational is divided into mortal and immortal. Thus the first object (the animal) is divided into two terms, the rational and the irrational, and the division of one of these terms, which says that the rational is divided into the mortal and the immortal, is a subdivision. However, division and additional division do not always occur, but in the case when the first division does not embrace everything. For example, an animal is divided into rational and irrational. But in both rational and irrational animals there is a characteristic: bipedal. Therefore an additional division is necessary, i.e., we make a second division of the same object, namely, the animal, and we say: the animal is divided into legless, two-legged, and four-legged.

There are eight ways of dividing on the following basis. Everything that is subject to division is divided either by itself, i.e., according to its substance, or according to its accidents. If something is divided by itself, then it is divided either as a thing or as a name. If as a thing, then either as a genus into species, as in the division of an animal into rational and irrational, or as a species into individuals, as in the division of man into Peter, Paul, and other individual men, or as a whole into parts.

At the same time, the latter division is of two kinds: either into similar parts, or into dissimilar parts. A thing is made up of similar parts, when its parts take the name and definition of both the whole and each other—for example, meat is divided into many pieces of meat, and each piece is called meat and takes the definition of meat. On the contrary, an object consists of parts that are not similar, when the separated parts do not accept either the name or the definition of either the whole or each other—for example, if Socrates is divided into arms, legs, and head. In fact, the leg or head separated from Socrates is no longer called Socrates, just as the foot of Socrates does not accept the definition of Socrates or the definition of the head.

Or as a homonymous name — on the denoted differences. And this division is again of two kinds, since the name designates either a whole or a part. The whole, such as the name: dog. This name signifies something whole, because it is used in the application of the terrestrial dog, and the celestial dog, and the sea dog, each of which is a whole, and not a part of the animal. The part when, for example, the name of the tongue is applied to the upper part of the sandals, and to the upper part of the flute, and to the taste organ of animals, all these are parts, not wholes.

This is how the division is made when the object is divided by itself. And according to accidents (a division is made), or when substance is divided into accidents, for example, when I say of men that some of them are white and others black, for men are substances, and white and black are accidents; or in the case where accident is divided into substances, for example, when I say that some of the white objects are animate, others inanimate, because the white color is an accident, and animate and inanimate objects are substances; or when an accident is divided into accidents, for example, when I say that some of the cold objects are white and dry, and others are black and damp, for cold, white, black, damp, dry, are all accidents.