The distinction of substance and accident and the analogy of being

Of those that exist, some are said of a subject, but are in no subject: as man is said of some subject, namely of some man, but is in no subject. Others, however, are in a subject, but are said of no subject. And I say that to be in a subject which, while it is in something not as a part, cannot exist apart from the thing in which it is. For example, some particular literacy is in a subject, namely in the soul, but is not said of any subject, and this whiteness is in a body as in its subject, for any color is in a body. Others both are said of and are in a subject. For example, knowledge is in the soul, and is said of a subject, say, of literacy. Still others neither are in a subject, nor are said of a subject, for example, some particular man, or some particular horse: for none of these is either in or is said of a subject. In general, individuals, and what are numerically one are said of no subject, but nothing prevents them from being in a subject, for some particular literacy is in a subject.