Logic I, Lesson 7: Substances & Accidents

Logic I, Lesson 7: Substances & Accidents

Summary: A substance is something that exists in itself and not in another. It can be an individual reality, such as the individual man Socrates, or a universal concept, such as "man" in general. An accident is something that exists, not in itself, but in a substance. It can be an individual reality, such as the particular fact that I am 6'1', or a universal concept, such as "height" in general.

From Aristotle's Categories 2 (notes added in brackets):

[Secondary or Universal Substances.] Of things themselves some are predicable of a subject, and are never present in a subject. Thus 'man' is predicable of the individual man, and is never present in a subject.

(By being 'present in a subject' I do not mean present as parts are present in a whole, but being incapable of existence apart from the said subject [e.g., as whiteness cannot exist apart from a white thing].)

[Primary or Individual Accidents.] Some things, again, are present in a subject, but are never predicable of a subject. For instance, a certain point of grammatical knowledge is present in the mind, but is not predicable of any subject; or again, a certain whiteness may be present in the body (for colour requires a material basis), yet it is never predicable of anything.

[Secondary or Universal Accidents.] Other things, again, are both predicable of a subject and present in a subject. Thus while knowledge is present in the human mind, ["knowledge"] is predicable of grammar [i.e., one can both say "grammar is knowledge" and "knowledge is in the mind"].

[Primary or Individual Substances.] There is, lastly, a class of things which are neither present in a subject nor predicable of a subject [i.e., because it is the subject], such as the individual man or the individual horse.

[Rejoinder.] But, to speak more generally, that which is individual and has the character of a unit [i.e., whether substance or accident] is never predicable of a subject. Yet in some cases there is nothing to prevent such [i.e., the individual accident] being present in a subject. Thus a certain point of grammatical knowledge is present in a subject.

From Averroes' Middle Commentary on Aristotle's Categories, Pt. 1, Ch. 2:

[Secondary or Universal Substances.] He said: some beings are predicated of a subject and are not in a subject. That is, some make known the substance and quiddity of everything of which they are predicated and in no way make anything external [i.e., accidental] to the substance of a subject known. This is the general [i.e., universal] substance, like animal and man. For if they are both predicated of something, they make known its substance and essence--nothing external to its essence.

[Primary or Individual Accidents.] Some are in a subject [...] and cannot be [...] in any way predicated of a subject [...]. This is the designated individual accident--like this designated blackness and this designated whiteness existing in this designated body, since every color is in a body.

[Secondary or Universal Accidents.] Some are predicated of a subject and are also in a subject [...]. This is the general [or universal] accident--like our predicating knowledge of the soul and of writing, for we say "writing is knowledge" and "knowledge is in the soul." So, when we predicate it of writing, it makes its substance known, since it is its genus and may appropriately be given in response to "what is writing?" When it is predicated of the soul and it is said "in the soul there is knowledge," it makes known something external to the soul's essence.

[Primary or Individual Substances.] Some are neither predicated of a subject--that is, as predicates that make its substance known--nor in a subject--that is, predicated of a subject so as to make anything external [i.e., accidental] to its substance known. And this is the designated individual substance, like Zayd and ‘Amr.* It is not predicated of anything in a natural manner, neither as a predicate which makes the substance of the subject known nor as a predicate that does not make it known.

[Rejoinder.] On the whole, substance, whether it be general or individual, is that which is not in a subject at all. And on the whole, accident, whether it be general or individual, is that which is in a subject. And on the whole, the general [i.e., universal], whether it be a substance or an accident, is that which is said of a subject [i.e., as a predicate]. On the whole, the individual, whether it be an accident or a substance, is that which is not said of a subject.

Thus universal substance is distinguished from individual substance in that universal substance is said of a subject and individual substance is not. And individual accident is distinguished from universal accident in that universal accident is said of a subject and individual accident is not.

[*NB. Whereas Aristotle typically uses the name "Socrates" as his example of an individual man, Averroes uses the names "Zayd" and "‘Amr," which are rather common names in Arabic.]