Book 9
4
All senses which are merely equivocal may be dismissed; for some are used by analogy, as in geometry,Cf. Aristot. Met. 5.12.11. and we call things possible or impossible because they are or are not in some particular way. But the potentialities which conform to the same type are all principles, and derive their meaning from one primary sense of potency, which is the source of change in some other thing, or in the same thing qua other.
5
One kind of potentiality is the power of being affected; the principle in the patient itself which initiates a passive change in it by the action of some other thing, or of itself qua other. Another is a positive state of impassivity in respect of deterioration or destruction by something else or by itself qua something else; i.e. by a transformatory principle—for all these definitions contain the formula of the primary sense of potentiality.
6
Again, all these potentialities are so called either because they merely act or are acted upon in a particular way, or because they do so well . Hence in their formulae also the formulae of potentiality in the senses previously described are present in some degree.
6
Clearly, then, in one sense the potentiality for acting and being acted upon is one (for a thing is capable both because it itself possesses the power of being acted upon, and also because something else has the power of being acted upon by it);
