ou genomenon ex oudenos (not made out of anything) is not equivalent to genomenon ek tou mêdenos (made out of nothing). The former notion would be applicable to a Creature created from eternity, if there were such: the latter would not. The former denies pre-existent material, the latter affirms a previous condition of nothingness. The former implies creation, the latter implies the lapse of a finite period since creation.
Of God and His Creatures: 2.38