And therefore the mathematician or any one else whose thoughts are much absorbed in some intellectual pursuit, must allow his body also to have due exercise, and practise gymnastic; and he who is careful to fashion the body, should in turn impart to the soul its proper motions, and should cultivate music and all philosophy, if he would deserve to be called truly fair and truly good. And the separate parts should be treated in the same manner, in imitation of the pattern of the universe; for as the body is heated and also cooled within by the elements which enter into it, and is again dried up and moistened by external things, and experiences these and the like affections from both kinds of motions, the result is that the body if given up to motion when in a state of quiescence is overmastered and perishes; but if any one, in imitation of that which we call the foster-mother and nurse of the universe, will not allow the body ever to be inactive, but is always producing motions and agitations through its whole extent, which form the natural defence against other motions both internal and external, and by moderate exercise reduces to order according to their affinities the particles and affections which are wandering about the body, as we have already said when speaking of the universe, he will not allow enemy placed by the side of enemy to stir up wars and disorders in the body, but he will place friend by the side of friend, so as to create health.

[88c] τὸν δὴ μαθηματικὸν ἤ τινα ἄλλην σφόδρα μελέτην διανοίᾳ κατεργαζόμενον καὶ τὴν τοῦ σώματος ἀποδοτέον κίνησιν͵ γυμναστικῇ προσομιλοῦντα͵ τόν τε αὖ σῶμα ἐπιμελῶς πλάττοντα τὰς τῆς ψυχῆς ἀνταποδοτέον κινήσεις͵ μουσικῇ καὶ πάσῃ φιλοσοφίᾳ προσχρώμενον͵ εἰ μέλλει δικαίως τις ἅμα μὲν καλός͵ ἅμα δὲ ἀγαθὸς ὀρθῶς κεκλῆσθαι. κατὰ δὲ ταὐτὰ ταῦτα καὶ τὰ μέρη θεραπευτέον͵ τὸ τοῦ παντὸς ἀπομιμούμενον εἶδος. [88d] τοῦ γὰρ σώματος ὑπὸ τῶν εἰσιόντων καομένου τε ἐντὸς καὶ ψυχομένου καὶ πάλιν ὑπὸ τῶν ἔξωθεν ξηραινομένου καὶ ὑγραινομένου καὶ τὰ τούτοις ἀκόλουθα πάσχοντος ὑπ΄ ἀμφοτέρων τῶν κινήσεων͵ ὅταν μέν τις ἡσυχίαν ἄγον τὸ σῶμα παραδιδῷ ταῖς κινήσεσι͵ κρατηθὲν διώλετο͵ ἐὰν δὲ ἥν τε τροφὸν καὶ τιθήνην τοῦ παντὸς προσείπομεν μιμῆταί τις καὶ τὸ σῶμα μάλιστα μὲν μηδέποτε ἡσυχίαν ἄγειν ἐᾷ͵ κινῇ δὲ καὶ σεισμοὺς ἀεί τινας ἐμποιῶν αὐτῷ [88e] διὰ παντὸς τὰς ἐντὸς καὶ ἐκτὸς ἀμύνηται κατὰ φύσιν κινήσεις καὶ μετρίως σείων τά τε περὶ τὸ σῶμα πλανώμενα παθήματα καὶ μέρη κατὰ συγγενείας εἰς τάξιν κατακοσμῇ πρὸς ἄλληλα͵ κατὰ τὸν πρόσθεν λόγον ὃν περὶ τοῦ παντὸς ἐλέγομεν͵ οὐκ ἐχθρὸν παρ΄ ἐχθρὸν τιθέμενον ἐάσει πολέμους ἐντίκτειν τῷ σώματι καὶ νόσους͵ ἀλλὰ φίλον παρὰ φίλον τεθὲν ὑγίειαν ἀπεργαζόμενον παρέξει.