Kitap 5
4
(c) All states in virtue of which things are unaffected generally, or are unchangeable, or cannot readily deteriorate, are called potencies. For things are broken and worn out and bent and in general destroyed not through potency but through impotence and deficiency of some sort; and things are unaffected by such processes which are scarcely or slightly affected because they have a potency and are potent and are in a definite state.
5
Since potency has all these meanings, potent (or capable) will mean (a) that which contains a source of motion or change (for even what is static is potent in a sense) which takes place in another thing, or in itself qua other. (b) That over which something else has a potency of this kind. (c) That which has the potency of changing things, either for the worse or for the better (for it seems that even that which perishes is capable of perishing; otherwise, if it had been incapable, it would not have perished. As it is, it has a kind of disposition or cause or principle which induces such an affection.
6
Sometimes it seems to be such as it is because it has something, and sometimes because it is deprived of something; but if privation is in a sense a state or habit, everything will be potent through having something; and so a thing is potent in virtue of having a certain habit or principle, and also in virtue of having the privation of that habit, if it can have privation; and if privation is not in a sense habit, the term potent is equivocal).
7
(d) A thing is potent if neither any other thing nor itself qua other contains a potency or principle destructive of it. (e) All these things are potent either because they merely might chance to happen or not to happen, or because they might do so well . Even in inanimate things this kind of potency is found; e.g. in instruments; for they say that one lyre can be played, and another not at all, if it has not a good tone.
