In a detailed and spirited critique, Professor James M. Humber has found my defence of the ontological argument unconvincing. Humber's case rests upon his claim that my ‘error’ is due to my ‘having accepted an incorrect definition of “physically necessary being” … ’. Now I do indeed claim that God must be conceived as a factuall necessary being, i.e. as eternally independent. I take the notion of God's aseity or eternal independence to be relatively straightforward and uncontroversial; it is accepted (...) as an essential component of the concept God by many philosophers who also insist that there is no acceptable form of demonstrative theism. Thus, it is widely held that ‘God is a factually necessary being’ does not imply ‘God is a logically necessary being’; that God is eternally independent does not imply that he exists in all possible worlds. But it is precisely this view that I have argued is incorrect. While I concur that there is an intelligible concept of God as factually necessary, I deny that the existence of such a being is logically contingent, a mere matter of empirical fact. Indeed, a rigorous inspection of the concept of an eternally independent being reveals that whether that concept is instantiated, i.e. whether there exists a being exemplifying that concept, is knowable a priori . My claim is in fact stronger than this. I argue that the existence of an eternal, independent, omniscient and omnipotent being is demonstrable by conceptual analysis. It is Humber's contention that my alleged demonstration of God's existence crumbles upon the discovery of the unacceptability of my definition of ‘factually necessary being’. Let us see. (shrink)