other; and in one sense that over which something else has such a potency; and in one sense that which has a potency of changing into something, whether for the worse or for the better (for even that which perishes is thought to be 'capable' of perishing, for it would not have perished if it had not been capable of it; but, as a matter of fact, it has a certain disposition and cause and principle which fits it to suffer this; — sometimes it is thought to be of this sort because it has something, sometimes because it is deprived of something; but if privation is in a sense 'having' or 'habit', everything will be capable by having something, so that things are capable both by having a positive habit and principle, and by having the privation of the positive principle, if it is possible to have a privation; and if privation is not in a sense 'habit', 'capable' is used in two distinct senses[1]); and a thing is capable in another sense because neither any other thing, nor itself qua other, has a potency or principle which can destroy it. Again, all these are capable either merely because the thing might chance to happen or not to happen, or because it might do so well. This sort of potency is found also in lifeless things, e.g. in instruments; for we say one lyre can be made to 'speak', and another cannot be made to 'speak' at all, if it has not a good tone.
Incapacity is privation of capacity — i.e. of such a principle as has been described — either in general or in the case of something that would naturally have the capacity, or even at the time when it would naturally already have it; for the senses in which we should call a boy and a man and a eunuch incapable of begetting are distinct. — Again, to either kind of capacity there is an opposite incapacity — both to that which only can produce movement and to that which can produce it well.
Some things, then, are called ἀδύνατα in virtue of this kind of incapacity, while others are so in another sense, i.e. in that in which we couple δυνατόν and ἀδύνατον.[2] The impossible
