to be straight. The principles of things that always come to be according to nature cannot be eternal. For if they transmit the nature they have to the things that come to be from them, and this nature is created, then the nature of the principles is also created, even if the manner of coming-to-be is changed and is different from that of the things from the principles. 43. From the same argument. It is necessary for the first mover to be one and eternal. For it has been shown that it is necessary for motion to exist always. And if it is always, it is necessary for it to be continuous; for that which is always is continuous; for that which is successive is not continuous. And if it is continuous, it is one; and one motion is that which is produced by one mover and one thing moved; for if another and another thing should cause motion, the motion is not continuous but successive. If the first mover causes the motion of locomotion, and the motion of locomotion is of the heaven, and the heaven is a natural body, and a natural body has within itself naturally the principle of its motion according to nature, then the heaven is moved superfluously by the first mover in the motion of locomotion; which motion, even if the first mover did not move it, it would be moved by itself, because it is the fifth element, having neither weight moving it downwards, nor lightness moving it upwards, but another, unnamed power moving it around the center. If the first mover moves the heaven with the motion of locomotion neither according to nature (for to move thus is superfluous) nor contrary to nature (for motion contrary to nature is secondary to motion according to nature), then nothing moves the heaven. If all motion, as it happens now, so also happened previously, and it happens now according to a change of that which is about to be, and that which is about to be was not yet before it came to be, and that which first is not, but is later, all this is created, and it is not possible for that which is created to be without beginning and eternal, then motion is not eternal and without beginning. 44. From the same argument. It is clear that locomotion is first. For 'first', just as in other cases, so also in the case of motion would be said in several ways. A thing is said to be prior if, when it does not exist, the others will not exist, while it can exist without the others, and prior in time, and prior in substance. That it is necessary for locomotion to be first. For there is no necessity for that which is in locomotion either to grow or to be altered, nor indeed to come to be or to perish; but none of these is possible without the continuous motion, which the first mover causes. Further, it is first in time; for it is possible for the eternal things alone to be moved with this motion. But in the case of a single one of the things that have generation, it is necessary for locomotion to be the last of the motions; for after coming to be, first there is growth and alteration, but locomotion is the motion of things already perfected. But it is necessary for something else to be in locomotion previously, which will also be the cause of generation for the things that are generated, not being generated itself, such as the begetter of the begotten, since generation might seem to be the first of the motions for this reason, that the thing must first come to be.
εἶναι εὐθεῖαν. Aἱ ἀρχαὶ τῶν κατὰ φύσιν ἀεὶ γινομένων ἀΐδιοι εἶναι οὐ δύνανται. Eἰ γὰρ ἣν ἔχουσι φύσιν ταύτην μεταδιδόασι τοῖς ἐξ αὐτῶν γιγνομένοις, γενητὴ δὲ αὕτη, γενητὴ ἄρα καὶ ἡ τῶν ἀρχῶν φύσις, εἰ καὶ ὁ τρόπος τῆς γε νέσεως ἐνήλλακται καὶ ἔστιν ἕτερος τῆς τῶν ἐξ ἀρχῶν. μγ. Ἐκ τοῦ αὐτοῦ λόγου. Ἀνάγκη εἶναί τι ἓν καὶ ἀΐδιον τὸ πρῶτον κινοῦν. ∆έ δεικται γὰρ ὅτι ἀνάγκη ἀεὶ κίνησιν εἶναι. Eἰ δὲ ἀεί, ἀνάγκη συνεχῆ εἶναι· καὶ γὰρ τὸ ἀεὶ συνεχές· τὸ γὰρ ἐφεξῆς οὐ συνεχές. Eἰ δὲ συνεχής, μία· μία δ' ἡ ὑφ' ἑνός τε κινοῦν τος καὶ ἑνὸς τοῦ κινουμένου· εἰ γὰρ ἄλλο καὶ ἄλλο κινήσει, οὐ συνεχὴς ἡ κίνησις ἀλλ' ἐφεξῆς. Eἰ τὸ πρῶτον κινοῦν τὴν κατὰ φορὰν κίνησιν, ἡ δὲ κατὰ φορὰν κίνησίς ἐστι τοῦ οὐρανοῦ, ὁ δὲ οὐρανός ἐστι φυσικὸν σῶμα, τὸ δὲ φυσικὸν σῶμα ἐν ἑαυτῷ ἔχει φυσικῶς τῆς κατὰ φύσιν κινήσεως τὴν ἀρχήν, περιττῶς ἄρα κινεῖται ὁ οὐρανὸς τοῦ πρώτου κινοῦντος τὴν κατὰ φορὰν κίνησιν· ἣν καὶ εἰ μὴ τὸ πρῶτον κινοῦν ἐκίνει αὐτόν, ἐκινεῖτο ἂν αὐτὸς ὑφ' ἑαυτοῦ, διὰ τὸ εἶναι αὐτὸν πέμπτον στοιχεῖον μήτε βαρύτητα ἔχον κι νοῦσαν αὐτὸν ἐπὶ τὸ κάτω, μήτε κουφότητα κινοῦσαν αὐτὸν ἐπὶ τὸ ἄνω, ἀλλὰ ἑτέραν δύναμιν ἀνώνυμον κινοῦσαν αὐτὸν περὶ τὸ μέσον. Eἰ τὸ πρῶτον κινοῦν τὴν κατὰ φορὰν κίνησιν τὸν οὐρανὸν οὔτε κατὰ φύσιν αὐτὸν κινεῖ (περιττὸν γὰρ τὸ οὕτως κινεῖν) οὔτε παρὰ φύσιν (δευτέρα γάρ ἐστι κίνησις ἡ παρὰ φύσιν τῆς κατὰ φύσιν κινήσεως), οὐκ ἄρα κινεῖ τι τὸν οὐρανόν. Eἰ πᾶσα κίνησις, ὡς γίνεται νῦν, οὕτως καὶ τὸ πρότερον ἐγίνετο, γίνεται δὲ νῦν κατὰ μεταβολὴν τοῦ μέλλοντος γίνεσθαι, τὸ δὲ μέλλον γίνεσθαι πρὸ τοῦ γενέσθαι οὔπω ἦν, τὸ δὲ πρῶτον μὲν οὐκ ὄν, ὕστερον δέ, γενητὸν τοῦτο πᾶν, τὸ δὲ γενητὸν ἄναρχόν τε καὶ ἀΐδιον οὐ δυνατὸν εἶναι, οὐκ ἄρα ἡ κίνησις ἀΐδιός τε καὶ ἄναρχος. μδ. Ἐκ τοῦ αὐτοῦ λόγου. Φανερὸν ὅτι ἡ φορὰ πρώτη. Τὸ γὰρ πρῶτον ὥσπερ ἐφ' ἑτέρων, οὕτως καὶ ἐπὶ κινήσεως ἂν λέγοιτο πλεοναχῶς. Λέγεται δὲ πρότερον, οὗ γε μὴ ὄντος οὐκ ἔσται τὰ ἄλλα, ἐκεῖνο δὲ ἄνευ τῶν ἄλλων, καὶ τὸ χρόνῳ, καὶ τὸ κατ' οὐσίαν. Ὅτι ἀνάγκη τὴν φορὰν εἶναι πρώτην. Oὐδὲ γὰρ μία ἀνάγκη οὔτε αὔξεσθαι οὔτε ἀλλοιοῦσθαι τὸ φερόμενον, οὐδὲ δὴ γίνεσθαι ἢ φθείρεσθαι· τούτων δὲ οὐδεμίαν ἐνδέχεται τῆς συνεχοῦς μὴ οὔσης, ἣν κινεῖ τὸ πρῶτον κινοῦν. Ἔτι χρόνῳ πρώτη· τοῖς γὰρ ἀϊδίοις μόνον ἐνδέχεται κινεῖσθαι ταύτην. Ἀλλ' ἐφ' ἑνὸς μὲν τῶν ἐχόντων τὴν γένεσιν τὴν φορὰν ὑστάτην ἀναγκαῖον εἶναι τῶν κινήσεων· μετὰ γὰρ τὸ γε νέσθαι πρῶτον αὔξησις καὶ ἀλλοίωσις, φορὰ δὲ ἤδη τε λειουμένων κίνησίς ἐστιν. Ἀλλὰ ἕτερον ἀνάγκη κινούμενον εἶναι κατὰ φορὰν πρότερον, ὃ καὶ τῆς γενέσεως αἴτιον ἔσται τοῖς γιγνομένοις, οὐ γιγνόμενον, οἷον τὸ γεννῆσαν τοῦ γεννηθέντος, ἐπεὶ δόξειεν ἂν ἡ γένεσις εἶναι πρώτη τῶν κινήσεων διὰ τοῦτο, ὅτι γενέσθαι δεῖ τὸ πρᾶγμα πρῶτον.