10.  The Father begat 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 Compare Athanasius (de Sententiâ Dionysii, § 23):  “the mind creates the word, being manifested in it, and the word shews the mind, having originated therein.”  Tertullian (adv. Prax. vii.):  “You will say what is a word but a voice and sound of the mouth, and (as the Grammarians teach) air when struck against, intelligible to the ear, but for the rest a sort of void, empty, and incorporeal thing.”  Cf. Athan. (de Synodis, § 12):  ἀνυπόστατον..  But we know Christ to have been begotten not as a word pronounced προφορικόν.  See Cat. iv. 8, note 9., but as a Word substantially existing ἐνυπόστατον. ibid.  So the Spirit is described in Cat. xvii. 5 “not uttered or breathed by the mouth and lips of the Father and the Son, nor dispersed into the air, but personally subsisting (ἐνυπόστατον).” and living; not spoken by the lips, and dispersed, but begotten of the Father eternally and ineffably, in substance ἐν ὑποστάσει..  For, In the beginning was the Word, and the Word was with God, and the Word was God John i. 1., 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 John viii. 38.:  the Word possessed of power, and reigning over all things:  for the Father hath committed all things unto the Son Matt. xi. 27; John v. 22..