Augustine in His Own Words
So from words we learn only words, or better, the sound and noise of words. For a word, unless it be a sign, cannot be a word; but I still cannot recognize it as a word until I know what it means, what it signifies, even though I have heard the word. Therefore, it is by knowing the realities that we also come to a knowledge of words whereas, by the sound of words, we do not even learn the words. For we do not learn words we already know, and, as for those which we do not know, we cannot profess to have learned them until we have seen their meaning. And this comes about not by hearing the sounds they make, but from a knowledge of the realities they signify. It is perfectly logical and true to conclude that whenever words are spoken, we either know or do not know what they mean. If we do know, they remind us rather than teach something to us. If we do not know, they cannot even remind us of something though they may lead us to inquire. . . .
(11.38) But as for all those things we understand, it is not the outward sound of a speaker's words that we consult, but the truth that presides over the mind itself within us, though we may have been led to consult it because of the words. Now, the One who is consulted and who is said to "dwell in the inner person" (Eph 3:14–17), He is the One who teaches us, namely, Christ, that is, "the unchangeable Power of God and everlasting wisdom" (1 Cor 1:23–24). This is the Wisdom that every rational soul does indeed consult, but Wisdom reveals itself to each one according to one's capacity to grasp it by reason of the good or evil dispositions of one's will. And if one is sometimes mistaken, this does not come about because of some defect on the part of the Truth that one consulted, just as it is not because of a defect in the light outside us that our bodily eyes are often deceived. We acknowledge that it is this light that we consult with regard to visible objects so that it may show them to us as far as we are able.
(12.40) When it is a question of things which we behold with the mind, namely, our intellect and reason, we give verbal expression to realities which we directly perceive as present in that inner light of truth which enlightens and delights the so-called "inner person." But, here again, if the one who hears my words sees those things oneself with that clear and inner eye of the soul, one knows the things I speak of by contemplating them oneself and not by my words. Therefore, even when I speak what is true and one sees what is true, it is not I who teach you. For one is being taught not by my words but by the realities themselves made manifest by the enlightening action of God from within.58
58. De magistro 11.36–12.40 (CCL 29:194–98); trans. Russell, FOTC 59:49–54. On this, see Gareth B. Matthews, "Knowledge and Illumination," in Cambridge Companion to Augustine, 171–85. The idea of Christ "the inner teacher" appears routinely in Augustine's preaching; for example, s. 134.1.1; s. 293A.6 (= Dolbeau 3); Jo. ev. tr. 3.15; ep. 2*.7 (Divjak).