8.  Think not therefore that this generation is human, nor as Abraham begat Isaac.  For in begetting Isaac, Abraham begat not what he would, but what another granted.  But in God the Father’s begetting there is neither ignorance nor intermediate deliberation The Arians appear to have made use of a dilemma:  If God begat with will and purpose, these preceded the begetting, and so ἦν ποτε ὅτε οὐκ ἦν, there was a time when the Son was not:  if without will and purpose, then He begat in ignorance and of necessity.  The answer is fully given by Athanasius (c. Arian. iii. 58–67, pp. 425–431 in this Series)..  For to say that He knew not what He was begetting is the greatest impiety; and it is no less impious to say, that after deliberation in time He then became a Father.  For God was not previously without a Son, and afterwards in time became a Father; but hath the Son eternally, having begotten Him not as men beget men, but as Himself only knoweth, who begat Him before all ages Very God.