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.

There is another way of dividing, namely, into objects originating from one object and relating to one object. From the one, namely, medicine, both the medical book and the medical instrument are derived, for they are called medical from one subject, medicine. To one object belong a medicine useful for health and food useful for health, for they have in mind one and the same object – health. As for objects derived from the same object, some of them derive their name from a certain cause, for example, the image of a man derives its name from a true cause, i.e., man; others because they were invented by someone: for example, a medical knife and similar objects.

Such is the general division of objects, according to which everything that admits of division can be divided: either as a genus into species, or as a species into individuals, or as a whole into parts, or as a homonymous name into signified differences, or as substance by accident, or as accident by substance, or as accident by accident, or as objects belonging to and relating to one and the same object. However, some do not recognize the division of a species into individuals as a division, preferring to call it calculus, because a division has two, three, very rarely four terms; but the species is divided into an infinite number of members; for individual people, for example, are an infinite number.

It is to be observed that no method of division [except the last] makes it possible to see what in the terms of division is antecedent in nature and what is subsequent, as well as what is higher and what is lower. But when we are divided according to descent from the same object or in relation to the same object, it is possible to see what is antecedent in nature and what is subsequent, and also what is higher and what is lower, from this proceeds its origin and name.

Chapter VII: Of the Antecedent by Nature. That which is posited together with the other, but does not posit it, which along with itself eliminates the other, but is not eliminated along with it, is called antecedent by nature. For example, the animal is by nature prior to man, for since the animal is eliminated and does not exist, then man will not necessarily exist, since man is an animal. If man is destroyed and does not exist, the existence of an animal is possible, because there will be a horse, a dog, and similar creatures that are animals. On the other hand, if man is posited, then an animal is certainly also posited, for man is an animal. But if an animal is posed, then a man is not necessarily posed, but a horse, a dog, and something like that can be relied upon, for they also are animals. Therefore Peter does not precede Paul by nature, or the rational animal precedes the irrational, for when Peter is removed and does not exist, Paul will exist, and when Paul is posited, Peter is not put together, just as when Peter is posited, Paul is not put together. In the same way, Peter is no more, that is, no more fully human or animal, than Paul, just as Paul is no more than Peter. But one remedy is more effective than another, and one medical book is more useful than another.

Chapter VIII. About the definition. A definition is a short speech expressing the nature of the subject, i.e., speech denoting this nature with a few words. For example, man is a rational animal, mortal, capable of understanding and comprehension. Many of the people have composed broad words about the nature of man, that is, long and pompous, but since they are not distinguished by brevity, they are therefore not definitions. On the other hand, there are also short words, such as sayings (apofqegmata), but since they do not express the nature of a thing, they are not definitions. And a name. Though it often expresses the nature of the subject matter, yet it is not a definition, for a name is one word (lexis), and a definition is speech (logos), and speech is composed of at least two distinct words. [A term is a name explained, and a name is a term in a condensed form]. The definition is made up of the genus and of the constituent (sustatikon), i.e., essential (ousiwdwn) differences. This can be seen in the definition of an animal: an animal is an animate substance possessing the faculty of perception. In this definition, substance is a genus, and animate and perceptual power are forming differences. It is composed (definition) of matter and form. For example, a statue is something that is made of copper and depicts a person. Thus, copper is matter, and "depicts man" is the form of a statue. In this case, matter corresponds to gender, and form corresponds to differences. A definition is also drawn up from the subject under study and the goal. For example, medicine is an art that has human bodies as its object, and has health as its goal. Here the subject of medicine is human bodies, and the goal is its health.

Description, on the other hand, is composed of non-essential attributes, i.e., properties and accidents. For example; Man is an animal capable of laughing, having an upright gait and flat nails. All these are insignificant signs. For this reason the description is called (in Greek) (upografh), since it gives a shadow of the object, as it were, and expresses not the essential being, but that which accompanies it. A descriptive definition is a mixture of essential and non-essential features of an object. For example, man is a rational animal with an erect gait and flat nails.

The definition (in Greek) is called (orismos) from the metaphor of land boundaries. As a boundary separates the property of each man from the property of another, so definition separates the nature of each thing from the nature of another.