Polybius, Histories 10.47 7-12
“There are many other examples which provide proof for this, but the clearest one of all is that from reading. In this case, if someone sets a person who is illiterate and unaccustomed to reading but not a fool and then place next to him a child who can read, give the child a book and order them to read what is written, it is clear that the man would not be able to believe that while reading one must first understand the image of each letter, then the value of its sound, and then the possible combinations with other letters, all things that require a great deal of time.
When he sees the child reading without pausing seven or five lines, he will not easily be able to believe that the child has not read the book before. He will straight out deny it if the reader observes the rhythm, the pauses, the rough breathings and the smooth breathings too. We should not bar for ourselves, then, anything which is useful because it appears to be difficult at first. No, we must use the force of habit, the means by which humans achieve all good things and even more so when it concerns the matters upon which our very safety depends.”
τοῦ δὲ τοιούτου λόγου παραδείγματα μὲν πολλὰ καὶ ἕτερα πρὸς πίστιν, ἐναργέστατον δὲ τὸ γινόμενον ἐπὶ τῆς ἀναγνώσεως. ἐπὶ γὰρ ἐκείνης, εἴ τις παραστησάμενος ἄνθρωπον ἄπειρον μὲν καὶ ἀσυνήθη γραμματικῆς, τἄλλα δ᾿ ἀγχίνουν, κἄπειτα παιδάριον ἕξιν ἔχον παραστήσας καὶ δοὺς βυβλίον κελεύοι λέγειν τὰ γεγραμμένα, δῆλον ὡς οὐκ ἂν δύναιτο πιστεῦσαι διότι <δεῖ> πρῶτον ἐπὶ τὰς ὄψεις τὰς ἑνὸς ἑκάστου τῶν γραμμάτων ἐπιστῆσαι τὸν ἀναγινώσκοντα, δεύτερον ἐπὶ τὰς δυνάμεις, τρίτον ἐπὶ τὰς πρὸς ἄλληλα συμπλοκάς, ὧν ἕκαστον ποσοῦ χρόνου τινὸς δεῖται.διόπερ ὅταν ἀνεπιστάτως θεωρῇ τὸ παιδάριον ὑπὸ τὴν ἀναπνοὴν ἑπτὰ καὶ πέντε στίχους συνεῖρον, οὐκ ἂν εὐχερῶς δύναιτο πιστεῦσαι διότι πρότερον οὗτος οὐκ ἀνέγνωκε τὸ βυβλίον· εἰ δὲ καὶ τὴν ὑπόκρισιν καὶ τὰς διαιρέσεις, ἔτι δὲ δασύτητας καὶ ψιλότητας δύναιτο συσσῴζειν, οὐδὲ τελέως. διόπερ οὐκ ἀποστατέον οὐδενὸς τῶν χρησίμων διὰ τὰς προφαινομένας δυσχερείας, προσακτέον δὲ τὴν ἕξιν, ᾗ πάντα τὰ καλὰ γίνεται θηρατὰ τοῖς ἀνθρώποις, ἄλλως τε καὶ περὶ τῶν τοιούτων, ἐν οἷς πολλάκις κεῖται τὸ συνέχον τῆς σωτηρίας.