Ἐγὼ δὲ τὴν ἐπὶ πλεῖον διαστολὴν πεποίημαι περὶ τούτων οὐχ ἕνεκα τῆς τῶν συγγραφέων ἐπιτιμήσεως, χάριν δὲ τῆς τῶν φιλομαθούντων ἐπανορθώσεως. τί γὰρ ὄφελος ἰατροῦ κάμνουσιν ἀγνοοῦντος τὰς αἰτίας τῶν περὶ τὰ σώματα διαθέσεων; τί δ’ ἀνδρὸς πραγματικοῦ μὴ δυναμένου συλλογίζεσθαι πῶς καὶ διὰ τί καὶ πόθεν ἕκαστα τῶν πραγμάτων τὰς ἀφορμὰς εἴληφεν; οὔτε γὰρ ἐκεῖνον εἰκὸς οὐδέποτε δεόντως συστήσασθαι τὰς τῶν σωμάτων θεραπείας οὔτε τὸν πραγματικὸν οὐδὲν οἷόν τε κατὰ τρόπον χειρίσαι τῶν προσπιπτόντων ἄνευ τῆς τῶν προειρημένων ἐπιγνώσεως. διόπερ οὐδὲν οὕτω φυλακτέον καὶ ζητητέον ὡς τὰς αἰτίας ἑκάστου τῶν συμβαινόντων, ἐπειδὴ φύεται μὲν ἐκ τῶν τυχόντων πολλάκις τὰ μέγιστα τῶν πραγμάτων, ἰᾶσθαι δὲ ῥᾷστόν ἐστι παντὸς τὰς πρώτας ἐπιβολὰς καὶ διαλήψεις.
(Polybius, Hist. 3.7.4-7)
In speaking at such length on this matter, my object has not been to censure previous writers, but to rectify the ideas of students. For of what use to the sick is a physician who is ignorant of the causes of certain conditions of the body? And of what use is a statesman who cannot reckon how, why, and whence each event has originated? The former will scarcely be likely to institute proper treatment for the body and it will be impossible for the latter without such knowledge to deal properly with circumstances. Nothing, therefore, should be more carefully guarded against and more diligently sought out than the first causes of each event, since matters of the greatest moment often originate from trifles, and it is the initial impulses and conceptions in every matter which are most easily remedied. (tr. William Roger Paton, revised by F.W. Walbank and Christian Habicht)