δὲ τὸν λόγον τοῦτον προκατατίθεμαι, ὅτι οἱ1 πολλοὶ τῶν ἀνθρώπων ὁκόταν τινὸς προτέρου ἀκούσωσι περί τινος ἐξηγευμένου, οὐκ ἀποδέχονται τῶν ὕστερον διαλεγομένων περὶ τούτων, οὐ γινώσκοντες ὅτι τῆς αὐτῆς ἐστὶ διανοίης γνῶναι τὰ ὀρθῶς εἰρημένα, ἐξευρεῖν τε τὰ μήπω εἰρημένα. ἐγὼ οὖν, ὥσπερ εἶπον, τοῖσι μὲν ὀρθῶς εἰρημένοισι προσομολογήσω· τὰ δὲ μὴ ὀρθῶς εἰρημένα δηλώσω 30ποῖα ἐστιν· ὁκόσα δὲ μηδὲ ἐπεχείρησε μηδεὶς τῶν πρότερον δηλῶσαι, ἐγὼ ἐπιδείξω καὶ ταῦτα 32οἷά ἐστι.
II. Φημὶ δὲ δεῖν τὸν μέλλοντα ὀρθῶς συγγράφειν περὶ διαίτης ἀνθρωπίνης2 πρῶτον μὲν παντὸς φύσιν ἀνθρώπου γνῶναι καὶ διαγνῶναι· γνῶναι μὲν ἀπὸ τίνων συνέστηκεν ἐξ ἀρχῆς, διαγνῶναι δὲ ὑπὸ τίνων μερῶν κεκράτηται· εἴτε γὰρ τὴν ἐξ ἀρχῆς σύστασιν μὴ γνώσεται, ἀδύνατος ἔσται τὰ ὑπ᾿ ἐκείνων γινόμενα γνῶναι· εἴτε μὴ γνώσεται τὸ ἐπικρατέον ἐν τῷ σώματι, οὐχ ἱκανὸς ἔσται τὰ συμφέροντα προσενεγκεῖν 10τῷ ἀνθρώπῳ. ταῦτα μὲν οὖν δεῖ3 γινώσκειν τὸν συγγράφοντα, μετὰ δὲ ταῦτα σίτων καὶ ποτῶν ἁπάντων, οἷσι διαιτώμεθα, δύναμιν ἥντινα ἕκαστα4 ἔχει καὶ τὴν κατὰ φύσιν καὶ τὴν δι᾿ ἀνάγκην καὶ τέχνην ἀνθρωπίνην.5 δεῖ γὰρ ἐπίστασθαι τῶν τε ἰσχυρῶν φύσει ὡς χρὴ τὴν δύναμιν ἀφαιρεῖσθαι, τοῖσι τε ἀσθενέσιν ὅκως χρὴ ἰσχὺν προστιθέναι διὰ τέχνης, ὅκου ἂν ὁ καιρὸς ἑκάστῳ6 παραγένηται. γνοῦσι δὲ τὰ εἰρημένα οὔπω αὐτάρκης ἡ θεραπείη τοῦ ἀνθρώπου, διότι οὐ δύναται
for the following reasons: most men, when they have already heard one person expounding a subject, refuse to listen to those who discuss it after him, not realising that it requires the same intelligence to learn what statements are correct as to make original discoveries. Accordingly, as I have said, I shall accept correct statements and set forth the truth about those things which have been incorrectly stated. I shall explain also the nature of those things which none of my predecessors has even attempted to set forth.
II. I maintain that he who aspires to treat correctly of human regimen must first acquire knowledge and discernment of the nature of man in general—knowledge of its primary constituents and discernment of the components by which it is controlled. For if he be ignorant of the primary constitution, he will be unable to gain knowledge of their effects; if he be ignorant of the controlling thing in the body he will not be capable of administering to a patient suitable treatment. These things therefore the author must know, and further the power possessed severally by all the foods and drinks of our regimen, both the power each of them possessed by nature and the power given them by the constraint of human art. For it is necessary to know both how one ought to lessen the power of these when they are strong by nature, and when they are weak to add by art strength to them, seizing each opportunity as it occurs. Even when all this is known, the care of a man is not yet complete, because