What makes my use of 'God' (i) have a referent at all and (ii) have the precise referent it has?This is the question. To what am I pointing when I say "God"? If I answer the question by way of a philosophical definition of divinity (Godhead), the rest is easy. I only have to establish whether the God worshipped by Christians and the God worshipped by Muslims agree with my definition of Godhead. If they both do, Muslims and Christians are worshipping the same God. If not, they don't.
If I answer the question by way of theology ("what are the essential things I have to say about God to make proper reference to him?"), the argument proceeds along the same lines. In fact, the distinction between a philosophical and a theological approach may be one of convenience because the two usually lead to opposite conclusions. But they do seem to me genuinely different at a deeper level in that the former seeks to abstract without reference to any specific religious tradition, while the latter believes this to be impossible or inadvisable.
Those pursuing a more philosophical approach might define "God" in the words of David Bentley Hart, The Experience of God, 7, as follows:
the infinite fullness of being, omnipotent, omnipresent, and omniscient, from whom all things come and upon whom all things depend for every moment of their existence, without whom nothing at all could exist.It follows that Christians and Muslims worship the same God, as do possibly Hindus and other polytheists who acknowledge one Godhead distinct from specific deities that in monotheistic traditions would more likely be referred to as angels rather than gods.
Those pursuing a more theological approach will tend towards the opposite conclusion. Christian theologians speak of God as being both one and (in another sense) three and both essentially so. If they reject the claim that God is essentially one and only accidentally (in another sense) three, they are likely to reject the claim that Muslims worship the same God, as Muslims do not worship the Trinity. Muslim theologians speak of God as the one whose eternal word is revealed in the Quran and to the extent that they consider "and Muhammed is his prophet" an essential part of defining "God", they must reject the claim that Christians worship the same God.
A third approach would be to define "God" biographically or, more accurately, by way of a history of revelation. In the context of the present discussion one might often find a reference to Abraham. God is "the God of Abraham," i.e. the one who revealed himself to Abraham. In and of itself such a reference to Abraham is not helping the discussion as much as many seem to think. Christians believe that Abraham worshipped the Trinity. Many, maybe most, Christians would qualify this by adding that Abraham had no clear conception of the Trinitarian nature of God. What is often overlooked that if it is true that Abraham had no access to Nicene-Constantinopolitan theology, neither did he have access to classical theist philosophy and the claim that Abraham worshipped the capital-B-Being is no less proper as well as problematic than the claim that he worshipped the Trinity.
Abraham, we believe, got to know God. His descendants received that knowledge and with further revelation a deeper knowledge of God was gained. Biography serves as an analogy here. God of course did not change but perception of him grew. The God of Abraham, Isaac and Jacob became the God who led Israel out of Egypt, YHWH who revealed himself through the Torah given to Moses, and climatically the one who raised Jesus from the dead.
Such a biographical approach is closer to the theological approach but without necessarily leading to the same conclusion. Say, by way of a rough analogy, A and B got to know G from childhood. B lost touch with G in adulthood. C got to know G only from adulthood (but of course learns about G's childhood in the process of making further acquaintance). D hears about G but never gets to meet him. Do they all refer to the same person?
A (the historical community of Jews who follow Christ) and C (Christians who joined the church from outside the synagogue) clearly do. B (the community of Jews who reject Christ) seems to refer to the same person as well but less reliably so, as their conception is based on childhood memories without a proper awareness of G's adult life. D arguably also refers to the same person at least in intent, although the link to the referent is more tenuous than with B to the extent that hear-say is different from memory. Lacking a genuine, contemporary acquaintance, neither B nor D can be said to be on speaking terms with G. (This is where some commenters focus on the word "worship".)
The analogy is merely meant to sketch the line of reasoning that would follow from an approach that identifies reference by way of tradition rather than philosophical postulate or theological thesis.
Which of these approaches is right or best? The interesting thing is that most commenters seem to assume that theirs is self-evidently the only approach there can be.
