§1.2#12 Περὶ μὲν οὖν τῆς τοῦ παντὸς φύσεως, εἴτʼ ἄπειρός ἐστι κατὰ τὸ μέγεθος εἴτε· πεπέρανται τὸν σύνολον ὄγκον, ὕστερον ἐπισκεπτέον·
2 Now concerning the nature of the whole, whether it is infinite in magnitude or finite in its total bulk, we must investigate later.
περὶ δὲ τῶν κατʼ εἶδος αὐτοῦ μορίων νῦν λέγω ἀρχὴν ποιησάμενοι τήνδε.
But concerning its parts according to species, let us speak now, making the following beginning.
πάντα γὰρ τὰ φυσικὰ σώματα καὶ μεγέθη καθʼ αὖτὰ κινητὰ λέγομεν εἶναι κατὰ τόπονʼ τὴν γὰρ φύσιν κινήσεως ἀρχὴν εἶναί φαμεν αὐτοῖς.
For we say that all natural bodies and magnitudes are in themselves movable in respect of place; for we say that nature is a principle of movement for them.
πᾶσα δὲ κίνησις ὅση κατὰ τόπον, ἣν καλοῦμεν φοράν, ἢ εὐθεῖα ἢ κύκλῳ ἢ ἐκ τούτων μικτή· ἀπίαι γὰρ αὗται δύο μόναι.
Now all movement in respect of place, which we call locomotion, is either straight, or circular, or a mixture of these; for these two alone are simple.
αἴτιον δʼ ὅτι καὶ τὰ μεγέθη ταῦτα ἀπλᾶ μόνον, ἥ τʼ εὐθεῖα καὶ ἡ περιφερής.
And the reason is that these magnitudes alone are simple, namely, the straight and the circular.
κύκλῳ μὲν οὖν ἐστὶν ἡ περὶ τὸ μέσον, εὐθεῖα δʼ ἡ ἄνω καὶ κάτω.
Now, circular movement is that around the center, and straight is that upward and downward.
λέγω δʼ ἄνω μὲν τὴν ἀπὸ τοῦ μέσου, κάτω δὲ τὴν ἐπὶ τὸ μέσον.
And by upward I mean the movement away from the center, and by downward that toward the center.
ὥστʼ ἀνάγκη πᾶσαν εἶναι τὴν ἀπλῆν φορὰν τὴν μὲν ἀπὸ τοῦ μέσου, τὴν δʼ ἐπὶ τὸ μέσον, τὴν δὲ περὶ τὸ μέσον.
So that it is necessary for all simple locomotion to be, on the one hand, away from the center, on the other hand, toward the center, and on the third hand, around the center.
καὶ ἔοικεν ἠκολουθηκέναι καὶ κατὰ λόγον τοῦτο τοῖς ἐξ ἀρχῆς· τό τε γὰρ σῶμα ἀπετελέσθη ἐν τρισὶ καὶ ἡ κίνησις αὐτοῦ.
And this seems to have followed also in accordance with reason what was said at the beginning; for as the body was completed in three dimensions, so also is its movement.
ἐπεὶ δὲ τῶν σωμάτων τὰ μέν ἐστιν ἀπλᾶ τὰ δὲ σύνθετα ἐκ τούτων (λέγω δʼ ἀπλᾶ ὅσα κινήσεως ἀρχὴν ἔχει κατὰ φύσιν, οἷον πῦρ καὶ γῆν καὶ τὰ τούτων εἴδη καὶ τὰ συγγενῆ τούτοις), ἀνάγκη καὶ τὰς κινήσεις εἶναι τὰς μὲν ἁπλὰς τὰς δὲ μικτάς πως, καὶ τῶν μὲν ἁπλῶν ἁπλᾶς, μικτὰς δὲ τῶν συνθέτων, κινεῖσθαι δὲ κατὰ τὸ ἐπικρατοῦν.
But since of bodies some are simple, and others are composite from these (and by simple I mean as many as have a principle of movement according to nature, such as fire and earth and their species and things cognate to them), it is necessary that movements also should be some simple and others somehow mixed, and those of simple bodies simple, and those of composite bodies mixed, and that they should move according to the prevailing element.
εἴπερ οὗν ἐστὶν ἁπλῆ κίνησις, ἁπλῆ δʼ ἡ κύκλῳ κίνησις, καὶ τοῷ τε ἁπλοῦ σώματος ἁπλῆ ἡ κίνησις καὶ ἡ ἁπλῆ κίνησις ἀπλοῷ σώματος (καὶ γὰρ ἂν συνθέτου ἡ, κατὰ τὸ ἐπικρατοῦν ἔσται), ἀναγκαῖον εἶναί τι σῶμα ἀπλοῦν ὃ πέφυκε φέρεσθαι τὴν κύκλῳ κίνησιν κατὰ τὴν αὐτοῦ φύσιν·
If then there is a simple movement, and circular movement is simple, and the movement of a simple body is simple, and a simple movement is that of a simple body (for even if it is the movement of a composite body, it will be according to the prevailing element), it is necessary that there should be some simple body which is naturally moved in a circle according to its own nature.
βίᾳ μὲν γὰρ ἐνδέχεται τὴν ἄλλου καὶ ἑτέρου, κατὰ φύσιν δὲ ἀδύνατον, εἴπερ μία ἑκάστου κίνησις ἡ κατὰ φύσιν τῶν ἁπλῶν.
For by force it is possible for it to perform the movement of another and different body, but according to nature it is impossible, if indeed the natural movement of each of the simple bodies is only one.
ἔτι εἰ ἡ παρὰ φύσιν ἐναντία τῇ κατὰ φύσιν καὶ ἓν ἐνὶ ἐναντίον, ἀνάγκη, ἐπεὶ ἁπλῆ ἡ ωύκλῳ, εἰ μὴ ἔσται κατὰ φύσιν τοῦ φερομένου σώματος, παρὰ φύσιν αὐτοῖ εἶναι.
Further, if movement contrary to nature is contrary to that according to nature, and one thing is contrary to one, it is necessary, since circular movement is simple, if it is not according to the nature of the body that is moved, that it should be contrary to its nature.
εἰ οὖν πῦρ ἢ ἄλλο τι τῶν τοιούτων ἐστὶ τὸ κύκλῳ φερόμενον, ἐναντία ἡ κατὰ φύσιν αὐτοῦ φορὰ ἔσται τῇ κύκλῳ.
If then the body that is moved in a circle is fire or some other such thing, its natural locomotion will be contrary to the circular.
ἀλλʼ ἦν ἐνὶ ἐναντίον· ὁ δʼ ἄνω καὶ κάτω ἀλλήλαις ἐναντίαι.
But one thing was contrary to one; and upward and downward movements are contrary to one another.