First motion comes from the soul; the heavens cannot rest
Where does the body's motion come from, if not the soul? The body is not a self-mover. Appeals to elemental lightness and heaviness do not give a first beginning of motion; they give a later account. Light and heavy things do come to rest in their places — so those qualities are not perpetual motion itself. Still less can thinking, judging, and forming opinions be the work of weight. The world, the sun, and the moon move by nature and cannot naturally stand still. So too the soul: by nature it is always in motion, and natural rest would be its undoing.
Greek
κινεῖσθαι ὑπὸ ἀκωήτου" νῦν δὲ ἀδύνατον, τὸ ἀκίνητον ὑπὸ ἀκπήτου κεεῖσϑαι" πόϑεν οὖν τῷ σώματι τὸ κινεῖσθαι, εἶ μὴ ἀπὸ τῆς ψυχῆς; οὐ γὰρ αὐτοκίνητόν ἐστι τὸ σῶμα. πρώτην οὖν γένεσιν κρήσεως ειη. πόϑεν οὖν --κνεῖσϑαι] αὑίωαι. ΜΝ. τ. Μοχ ἴθεσι, ἐπὰ νχῖς.' πρώτην οὖν πρώτην γοῦν. Α.α. Μο κήησιν γενέσεως, Μ. τ. εἴ μὲν γὰρ τὰ μὴ κινούμενον ἐκίνει πρώτην τὰ αἰε Ι. ἐξηγεῖται. πόϑεν] ἴπιοτ ἧπο Ἦαεο γοοη]νυ]α βἰιήῖε: πόϑεν οὖν τὲ κινεῖσϑαι εἰ μὴ απὸ ψυχῆς; οὐ γὰρ αὐτοκίνητόν ἐστὲ τὸ σῶμα. Ν. δεί ο απιε ]υσία κοῦφα ὄντα τῇ φύσει. Ὦ.1. φύσει α Ὀεῖι. Ναὶ), Λίοκ ἡ απιο κουφότης αἰνεῖι. ΝΜ. τ. οἳ ἵπιετ κίνησίς ἐστιν ει οὐδέποτε αὐάῑι: ἀφ᾽ ἑαυτῶν δὲ κινεῖται. Ν. Κόησίς ἐστι τεδε ϊάλε Οοιι. εαυ ε. Οστιε ἵια οχρϊσαπάωπ.