10 The Father begot the Son, not as among men mind begets word. For the mind is substantially existent in us; but the word when spoken is dispersed into the air and comes to an end. But we know Christ to have been begotten not as a word pronounced, but as a Word substantially existing and living; not spoken by the lips, and dispersed, but begotten of the Father eternally and ineffably, in substance. For, In the beginning was the Word, and the Word was with God, and the Word was God, sitting at God's right hand—the Word understanding the Father's will, and creating all things at His bidding: the Word, which came down and went up; for the word of utterance when spoken comes not down, nor goes up; the Word speaking and saying, The things which I have seen with My Father, these I speak: the Word possessed of power, and reigning over all things: for the Father has committed all things unto the Son.
Source: Catechetical Lectures (New Advent)