Hippocrates, De diaeta

87. Ὁκόσα μὲν οὖν τῶν ἐνυπνίων θεῖά ἐστι καὶ προσημαίνει τινὰ συμβησόμενα ἢ πόλεσιν ἢ τῷ ἰδιώτῃ λαῷ ἢ κακὰ ἢ ἀγαθὰ μὴ δι’ αὐτῶν ἁμαρτίην, εἰσὶν οἳ κρίνουσι περὶ τῶν τοιούτων ἀκριβῆ τέχνην ἔχοντες· ὁκόσα δὲ ἡ ψυχὴ τοῦ σώματος παθήματα προσημαίνει, πλησμονῆς ἢ κενώσιος ὑπερβολὴν τῶν ξυμφύτων, ἢ μεταβολὴν τῶν ἀηθέων, κρίνουσι μὲν καὶ ταῦτα, καὶ τὰ μὲν τυγχάνουσι, τὰ δὲ ἁμαρτάνουσι, καὶ οὐδέτερα τούτων γινώσκουσι, διότι γίνεται, οὔθ’ ὅ τι ἂν ἐπιτύχωσιν, οὔθ’ ὅ τι ἂν ἁμάρτωσι· φυλάσσεσθαι δὲ παραινεῦντες, μή τι κακὸν λάβῃ, οὐ διδάσκουσιν ὡς χρὴ φυλάξασθαι, ἀλλὰ θεοῖσιν εὔξασθαι κελεύουσι. Καὶ τὸ μὲν εὔχεσθαι πρέπον καὶ λίην ἐστὶν ἀγαθόν· δεῖ δὲ καὶ αὐτὸν ξυλλαμβάνοντα τοὺς θεοὺς ἐπικαλέεσθαι.

87. Now, as for dreams that are divine and foretell things that will happen, whether to cities or to private persons, bad or good, not through their own fault, there are those who judge such matters, having an exact art. But as for the dreams in which the soul foretells affections of the body, an excess of repletion or of depletion of what is natural to it, or a change to things it is unaccustomed to, they judge these too, and sometimes they hit the mark and sometimes they miss, and in neither case do they know why it happens, either when they succeed or when they fail; and while advising [people] to be on their guard lest some harm befall them, they do not teach how one should guard oneself, but bid them pray to the gods. And praying is indeed fitting and very good; but one must also lend a hand oneself while calling upon the gods.