Now of all motions that is the best which is produced in a thing by itself, for it is most akin to the motion of thought and of the universe; but that motion which is caused by others is not so good, and worst of all is that which moves the body, when at rest, in parts only and by some external agency. Wherefore of all modes of purifying and reuniting the body the best is gymnastic; the next best is a surging motion, as in sailing or any other mode of conveyance which is not fatiguing; the third sort of motion may be of use in a case of extreme necessity, but in any other will be adopted by no man of sense: I mean the purgative treatment of physicians; for diseases unless they are very dangerous should not be irritated by medicines, since every form of disease is in a manner akin to the living being, whose complex frame has an appointed term of life. For not the whole race only, but each individual-barring inevitable accidents-comes into the world having a fixed span, and the triangles in us are originally framed with power to last for a certain time, beyond which no man prolong his life. And this holds also of the constitution of diseases; if any one regardless of the appointed time tries to subdue them by medicine, he only aggravates and multiplies them. Wherefore we ought always to manage them by regimen, as far as a man can spare the time, and not provoke a disagreeable enemy by medicines.

[89a] τῶν δ΄ αὖ κινήσεων ἡ ἐν ἑαυτῷ ὑφ΄ αὑτοῦ ἀρίστη κίνησις - μάλιστα γὰρ τῇ διανοητικῇ καὶ τῇ τοῦ παντὸς κινήσει συγγενής - ἡ δὲ ὑπ΄ ἄλλου χείρων· χειρίστη δὲ ἡ κειμένου τοῦ σώματος καὶ ἄγοντος ἡσυχίαν δι΄ ἑτέρων αὐτὸ κατὰ μέρη κινοῦσα. διὸ δὴ τῶν καθάρσεων καὶ συστάσεων τοῦ σώματος ἡ μὲν διὰ τῶν γυμνασίων ἀρίστη͵ δευτέρα δὲ ἡ διὰ τῶν αἰωρήσεων κατά τε τοὺς πλοῦς καὶ ὅπῃπερ ἂν ὀχήσεις ἄκοποι γίγνωνται· [89b] τρίτον δὲ εἶδος κινήσεως σφόδρα ποτὲ ἀναγκαζομένῳ χρήσιμον͵ ἄλλως δὲ οὐδαμῶς τῷ νοῦν ἔχοντι προσδεκτέον͵ τὸ τῆς φαρμακευτικῆς καθάρσεως γιγνόμενον ἰατρικόν. τὰ γὰρ νοσήματα͵ ὅσα μὴ μεγάλους ἔχει κινδύνους͵ οὐκ ἐρεθιστέον φαρμακείαις. πᾶσα γὰρ σύστασις νόσων τρόπον τινὰ τῇ τῶν ζῴων φύσει προσέοικε. καὶ γὰρ ἡ τούτων σύνοδος ἔχουσα τεταγμένους τοῦ βίου γίγνεται χρόνους τοῦ τε γένους σύμπαντος͵ καὶ καθ΄ αὑτὸ τὸ ζῷον εἱμαρμένον ἕκαστον ἔχον τὸν βίον φύεται͵ χωρὶς τῶν ἐξ ἀνάγκης παθημάτων· [89c] τὰ γὰρ τρίγωνα εὐθὺς κατ΄ ἀρχὰς ἑκάστου δύναμιν ἔχοντα συνίσταται μέχρι τινὸς χρόνου δυνατὰ ἐξαρκεῖν͵ οὗ βίον οὐκ ἄν ποτέ τις εἰς τὸ πέραν ἔτι βιῴη. τρόπος οὖν ὁ αὐτὸς καὶ τῆς περὶ τὰ νοσήματα συστάσεως· ἣν ὅταν τις παρὰ τὴν εἱμαρμένην τοῦ χρόνου φθείρῃ φαρμακείαις͵ ἅμα ἐκ σμικρῶν μεγάλα καὶ πολλὰ ἐξ ὀλίγων νοσήματα φιλεῖ γίγνεσθαι. διὸ παιδαγωγεῖν δεῖ διαίταις πάντα τὰ τοιαῦτα͵ καθ΄ ὅσον ἂν ᾖ τῳ σχολή͵ [89d] ἀλλ΄ οὐ φαρμακεύοντα κακὸν δύσκολον ἐρεθιστέον.