I have been arguing that whether 'God' and equivalents as used by Jews, Christians, and Muslims refer to the same being depends on one's philosophy of language. In particular, I suggested that only on a causal theory of names could one maintain that their respective references are to the same entity. The causal theory of names, however, strikes me as not very plausible. Here is one consideration among several.
The causal theory of names of Saul Kripke et al. requires that there be an initial baptism of the target of reference, a baptism at which the name is first introduced. This can come about by ostension: Pointing to a newly acquired kitten, I bestow upon it the moniker, 'Mungojerrie.' Or it can come about by the use of a reference-fixing definite description: Let 'Neptune' denote the celestial object responsible for the perturbation of the orbit of Uranus. In the second case, it may be that the object whose name is being introduced is not itself present at the baptismal ceremony. What is present, or observable, are certain effects of the object hypothesized. (See Saul Kripke Naming and Necessity, Harvard 1980 p. 79, n. 33 and p. 96, n. 42.)
As I understand it, a necessary condition for successful reference on the causal theory is that a speaker's use of a name be causally connected (perhaps indirectly) with the object referred to. We can refer to objects only if we stand in some causal relation to them (direct or indirect). So my use of 'God' refers to God not because there is something that satisfies the definite description or disjunction of definite descriptions that unpack the sense of 'God' as used by me and others in my linguistic community, but because my use of 'God' can be traced back though a long causal chain to an initial baptism, as it were, of God by, say, Abraham.
If this is what the causal theory (or at least the Kripkean version thereof) requires, then the theory rules out all reference to abstracta: Fregean propositions, numbers, sets, etc. But it also rules out reference to future events.
Suppose meteorologists predict a hurricane that has the power to wipe out New Orleans a second time. Conservatives to a man and a woman, they introduce the name 'Hillary' for this horrendous event, and they introduce it via some appropriately complex definite description. (They can't point to it since it doesn't yet exist.) The meteorologists continue with their work using 'Hillary' for the event in question. Since the event lies in the future, there is no question of its causing directly or indirectly any use of the name 'Hillary.' Nor is there any question of the name's being introduced on the basis of effects of the event.
What we seem to have here is a legitimate use of a proper name that cannot be accounted for by the causal theory. For the causal theory rules out reference to a thing or event to which one does not stand in a causal relation. This suggests that there is something very wrong with the theory. (See John Searle, Intentionality, Cambridge 1983, p. 241.)
Admittedly, the above Searle-y objection is not compelling, relying as it does on controversial assumptions about the nature of time. A presentist will probably not be impressed by it. If the present alone exists, then future events do not, in which case there can be no reference to them, assuming that one can successfully refer only to what exists.
Question for Kripkeans: Isn't "initial baptism" pleonastic? Or does Kripke allow for subsequent baptisms of a thing?