§5.12δύναμις λέγεται ἡ μὲν ἀρχὴ κινήσεως ἢ μεταβολῆς ἡ ἐν ἑτέρῳ ἢ ᾗ ἕτερον, οἷον ἡ οἰκοδομικὴ δύναμίς ἐστιν ἣ οὐχ ὑπάρχει ἐν τῷ οἰκοδομουμένῳ, ἀλλʼ ἡ ἰατρικὴ δύναμις οὖσα ὑπάρχοι ἂν ἐν τῷ ἰατρευομένῳ, ἀλλʼ οὐχ ᾗ ἰατρευόμενος.
"Power" is said, in one sense, of a beginning of movement or change in another, or qua other; for example, the art of building is a power which does not exist in the thing being built, but the art of medicine, being a power, might exist in the person being treated, but not qua person being treated.
ἡ μὲν οὖν ὅλως ἀρχὴ μεταβολῆς ἢ κινήσεως λέγεται δύναμις ἐν ἑτέρῳ ἢ ᾗ ἕτερον, ἡ δʼ ὑφʼ ἑτέρου ἢ ᾗ ἕτερον (καθʼ ἣν γὰρ τὸ πάσχον πάσχει τι, ὁτὲ μὲν ἐὰν ὁτιοῦν, δυνατὸν αὐτό φαμεν εἶναι παθεῖν, ὁτὲ δʼ οὐ κατὰ πᾶν πάθος ἀλλʼ ἂν ἐπὶ τὸ βέλτιον)·
Therefore, on the one hand, a beginning of change or movement in general is called a power in another, or qua other. On the other hand, [a power is called] that which is by another, or qua other (for according to this, that which is acted upon is acted upon in some way; sometimes, if it can be acted upon in any way at all, we say it is capable of being acted upon, and sometimes not in respect of every affection, but if it is towards the better).
ἔτι ἡ τοῦ καλῶς τοῦτʼ ἐπιτελεῖν ἢ κατὰ προαίρεσιν· ἐνίοτε γὰρ τοὺς μόνον ἂν πορευθέντας ἢ εἰπόντας, μὴ καλῶς δὲ ἢ μὴ ὡς προείλοντο, οὔ φαμεν δύνασθαι λέγειν ἢ βαδίζειν· ὁμοίως δὲ καὶ ἐπὶ τοῦ πάσχειν.
Further, the power of performing this well or according to choice; for sometimes those who have merely walked or spoken, but not well or not as they chose, we say are not able to speak or walk; and similarly also in the case of being acted upon.
ἔτι ὅσαι ἕξεις καθʼ ἃς ἀπαθῆ ὅλως ἢ ἀμετάβλητα ἢ μὴ ῥᾳδίως ἐπὶ τὸ χεῖρον εὐμετακίνητα, δυνάμεις λέγονται· κλᾶται μὲν γὰρ καὶ συντρίβεται καὶ κάμπτεται καὶ ὅλως φθείρεται οὐ τῷ δύνασθαι ἀλλὰ τῷ μὴ δύνασθαι καὶ ἐλλείπειν τινός· ἀπαθῆ δὲ τῶν τοιούτων ἃ μόλις καὶ ἠρέμα πάσχει διὰ δύναμιν καὶ τῷ δύνασθαι καὶ τῷ ἔχειν πώς.
Further, all those states according to which things are entirely unaffected or unchangeable, or not easily changeable into the worse, are called powers; for a thing is broken, crushed, bent, and in general destroyed, not by being capable, but by being incapable and lacking something; while those things are unaffected by such actions which are scarcely and slightly acted upon because of a power, and by being capable and being in a certain state.
λεγομένης δὲ τῆς δυνάμεως τοσαυταχῶς, καὶ τὸ δυνατὸν ἕνα μὲν τρόπον λεχθήσεται τὸ ἔχον κινήσεως ἀρχὴν ἢ μεταβολῆς (καὶ γὰρ τὸ στατικὸν δυνατόν τι) ἐν ἑτέρῳ ἢ ᾗ ἕτερον, ἕνα δʼ ἐὰν ἔχῃ τι αὐτοῦ ἄλλο δύναμιν τοιαύτην, ἕνα δʼ ἐὰν ἔχῃ μεταβάλλειν ἐφʼ ὁτιοῦν δύναμιν, εἴτʼ ἐπὶ τὸ χεῖρον εἴτʼ ἐπὶ τὸ βέλτιον (καὶ γὰρ τὸ φθειρόμενον δοκεῖ δυνατὸν εἶναι φθείρεσθαι, ἢ οὐκ ἂν φθαρῆναι εἰ ἦν ἀδύνατον· νῦν δὲ ἔχει τινὰ διάθεσιν καὶ αἰτίαν καὶ ἀρχὴν τοῦ τοιούτου πάθους· ὁτὲ μὲν δὴ τῷ ἔχειν τι δοκεῖ, ὁτὲ δὲ τῷ ἐστερῆσθαι τοιοῦτον εἶναι· εἰ δʼ ἡ στέρησίς ἐστιν ἕξις πως, πάντα τῷ ἔχειν ἂν εἴη τι, ὥστε τῷ τε ἔχειν ἕξιν τινὰ καὶ ἀρχήν ἐστι δυνατὸν καὶ τῷ ἔχειν τὴν τούτου στέρησιν, εἰ ἐνδέχεται ἔχειν στέρησιν· εἰ δὲ μή, ὁμωνύμως)· ἕνα δὲ τῷ μὴ ἔχειν αὐτοῦ δύναμιν ἢ ἀρχὴν ἄλλο ἢ ᾗ ἄλλο φθαρτικήν.
Since power is said in so many ways, "capable" also will be said in one way of that which has a beginning of movement or change (for indeed that which can produce rest is also something capable) in another, or qua other; and in another way if something else has such a power over it; and in another way if it has a power to change into anything whatever, whether into the worse or into the better (for even that which is destroyed seems to be capable of being destroyed, or it would not be destroyed if it were impossible; but as it is, it has a certain disposition and cause and beginning of such an affection; so sometimes it seems to be capable by having something, and sometimes by being deprived of it; but if deprivation is in a way a state, all things would be capable by having something, so that a thing is capable both by having a certain state and beginning, and by having the deprivation of this, if it is possible to have a deprivation; and if not, homonymously); and in another way because something else does not have a destructive power or beginning over it, or qua other.
ἔτι δὲ ταῦτα πάντα ἢ τῷ μόνον ἂν συμβῆναι γενέσθαι ἢ μὴ γενέσθαι, ἢ τῷ καλῶς.
Further, all these are so called either by the fact that it might merely happen to come to be or not to come to be, or by the fact that it does so well.
καὶ γὰρ ἐν τοῖς ἀψύχοις ἔνεστιν ἡ τοιαύτη δύναμις, οἷον ἐν τοῖς ὀργάνοις· τὴν μὲν γὰρ δύνασθαί φασι φθέγγεσθαι λύραν, τὴν δʼ οὐδέν, ἂν ᾖ μὴ εὔφωνος.
For indeed such a power exists in inanimate things, as in instruments; for they say one lyre is able to sound, and another not at all, if it is not sweet-toned.
ἀδυναμία δὲ ἐστὶ στέρησις δυνάμεως καὶ τῆς τοιαύτης ἀρχῆς οἵα εἴρηται, ἢ ὅλως ἢ τῷ πεφυκότι ἔχειν, ἢ καὶ ὅτε πέφυκεν ἤδη ἔχειν· οὐ γὰρ ὁμοίως ἂν φαῖεν ἀδύνατον εἶναι γεννᾶν παῖδα καὶ ἄνδρα καὶ εὐνοῦχον.
"Incapacity" is the deprivation of power and of such a beginning as has been mentioned, either entirely, or to that which is natural to have it, or even when it is already natural to have it; for they would not say in the same way that a boy, a man, and a eunuch are incapable of begetting.
ἔτι δὲ καθʼ ἑκατέραν δύναμιν ἔστιν ἀδυναμία ἀντικειμένη, τῇ τε μόνον κινητικῇ καὶ τῇ καλῶς κινητικῇ.
Further, to each power there is an opposite incapacity, both to that which is merely causative of movement and to that which does so well.
καὶ ἀδύνατα δὴ τὰ μὲν κατὰ τὴν ἀδυναμίαν ταύτην λέγεται, τὰ δὲ ἄλλον τρόπον, οἷον δυνατόν τε καὶ ἀδύνατον, ἀδύνατον μὲν οὗ τὸ ἐναντίον ἐξ ἀνάγκης ἀληθές (οἷον τὸ τὴν διάμετρον σύμμετρον εἶναι ἀδύνατον ὅτι ψεῦδος τὸ τοιοῦτον οὗ τὸ ἐναντίον οὐ μόνον ἀληθὲς ἀλλὰ καὶ ἀνάγκη· τὸ ἄρα σύμμετρον οὐ μόνον ψεῦδος ἀλλὰ καὶ ἐξ ἀνάγκης ψεῦδος)· τὸ δʼ ἐναντίον τούτῳ, τὸ δυνατόν, ὅταν μὴ ἀναγκαῖον ᾖ τὸ ἐναντίον ψεῦδος εἶναι, οἷον τὸ καθῆσθαι ἄνθρωπον δυνατόν· οὐ γὰρ ἐξ ἀνάγκης τὸ μὴ καθῆσθαι ψεῦδος.
And "impossible" things, on the one hand, are so called according to this incapacity, but on the other hand, in another way, as "possible" and "impossible" are used: namely, impossible is that of which the contrary is of necessity true (for example, that the diagonal of a square is commensurate is impossible, because such a statement is false, the contrary of which is not only true but also necessary; therefore, that it is commensurate is not only false but also of necessity false); and the contrary to this, the possible, is when it is not necessary that the contrary is false, as for a man to sit is possible; for that he is not sitting is not of necessity false.
τὸ μὲν οὖν δυνατὸν ἕνα μὲν τρόπον, ὥσπερ εἴρηται, τὸ μὴ ἐξ ἀνάγκης ψεῦδος σημαίνει, ἕνα δὲ τὸ ἀληθές, ἕνα δὲ τὸ ἐνδεχόμενον ἀληθὲς εἶναι.
The possible, then, in one way, as has been said, signifies that which is not of necessity false, in another way that which is true, and in another way that which can be true.
κατὰ μεταφορὰν δὲ ἡ ἐν γεωμετρίᾳ λέγεται δύναμις.
And in geometry, "power" is said by metaphor.
ταῦτα μὲν οὖν τὰ δυνατὰ οὐ κατὰ δύναμιν· τὰ δὲ λεγόμενα κατὰ δύναμιν πάντα λέγεται πρὸς τὴν πρώτην· αὕτη δʼ ἐστὶν ἀρχὴ μεταβολῆς ἐν ἄλλῳ ἢ ᾗ ἄλλο.
Now these possible things are not possible in respect of a power; but the things said in respect of a power are all so called in relation to the first; and this is a beginning of change in another, or qua other.
τὰ γὰρ ἄλλα λέγεται δυνατὰ τῷ τὰ μὲν ἔχειν αὐτῶν ἄλλο τι τοιαύτην δύναμιν τὰ δὲ μὴ ἔχειν τὰ δὲ ὡδὶ ἔχειν.
For other things are called capable because some of them have another thing which has such a power over them, others because they do not have it, and others because they have it in a certain way.
ὁμοίως δὲ καὶ τὰ ἀδύνατα.
And similarly also with impossible things.
ὥστε ὁ κύριος ὅρος τῆς πρώτης δυνάμεως ἂν εἴη ἀρχὴ μεταβλητικὴ ἐν ἄλλῳ ἢ ᾗ ἄλλο.
So that the primary definition of the first power would be: a beginning of change in another, or qua other.