Things are said to ‘be’ (1) in an accidental sense, (2) by their own nature.

(1) In an accidental sense, e.g. we say ‘the righteous doer is musical’, and ‘the man is musical’, and ‘the musician is a man’, just as we say ‘the musician builds’, because the builder happens to be musical or the musician to be a builder; for here ‘one thing is another’ means ‘one is an accident of another’. So in the cases we have mentioned; for when we say ‘the man is musical’ and ‘the musician is a man’, or ‘he who is pale is musical’ or ‘the musician is pale’, the last two mean that both attributes are accidents of the same thing; the first that the attribute is an accident of that which is, while ‘the musical is a man’ means that ‘musical’ is an accident of a man. (In this sense, too, the not-pale is said to be, because that of which it is an accident is.) Thus when one thing is said in an accidental sense to be another, this is either because both belong to the same thing, and this is, or because that to which the attribute belongs is, or because the subject which has as an attribute that of which it is itself predicated, itself is.

(2) The kinds of essential being are precisely those that are indicated by the figures of predication; for the senses of ‘being’ are just as many as these figures. Since, then, some predicates indicate what the subject is, others its quality, others quantity, others relation, others activi............