Accordingly, the word that sounds outwardly is the sign of the word that gives light inwardly; which latter has the greater claim to be called a word. For that which is uttered with the mouth of the flesh, is the articulate sound of a word; and is itself also called a word, on account of that to make which outwardly apparent it is itself assumed. For our word is so made in some way into an articulate sound of the body, by assuming that articulate sound by which it may be manifested to men's senses, as the Word of God was made flesh, by assuming that flesh in which itself also might be manifested to men's senses. And as our word becomes an articulate sound, yet is not changed into one; so the Word of God became flesh, but far be it from us to say He was changed into flesh. For both that word of ours became an articulate sound, and that other Word became flesh, by assuming it, not by consuming itself so as to be changed into it. And therefore whoever desires to arrive at any likeness, be it of what sort it may, of the Word of God, however in many respects unlike, must not regard the word of ours that sounds in the ears, either when it is uttered in an articulate sound or when it is silently thought. For the words of all tongues that are uttered in sound are also silently thought, and the mind runs over verses while the bodily mouth is silent. And not only the numbers of syllables, but the tunes also of songs, since they are corporeal, and pertain to that sense of the body which is called hearing, are at hand by certain incorporeal images appropriate to them, to those who think of them, and who silently revolve all these things.
[St. Augustine, De Trinitate XV, chapter 11.]