The problem with PRmerger’s idea is that it would seem to make God into a sort of flickering light or shape-shifting, amorphous pseudo-being, which is of course not true of the Christian God (that is to say, the true God) at all. Our God was incarnate of the Holy Spirit and of the Virgin Mary and became man, and all of those other things we are supposed to affirm in the Creed. He was substantial. He ate and drank, talked, wept, etc. He was at any rate
not a collection of abstract attributes, and there was neither falsehood nor sin in Him. But instead we see the modern Catholic (?) view to be something else, wherein if some belief system that is not Christianity nonetheless says of their god that he/she/it is ____ (some adjective that Christians may also apply to the true God), then the two belief systems, no matter what else they may espouse are therefore worshiping the true God. This makes no sense and is an abuse of the idea of the
spermatikos logos (the Word in seed form) to be found most prominently in the writings of Justin Martyr (d. 165), which says that there are aspects (clues, foreshadowings, etc.) of Christ and hence of the truth in every belief system. While we would most definitely affirm that about Islam, it is too far to say, therefore, that since Muslims or Jews or whoever say this or that about their god or gods that we must all be worshiping the same God. Either God is above the attributes we recognize as pertaining to Him with our limited languages and intellects, or He is not. Perhaps this is why Orthodoxy embraces apophatic theology rather than purely cataphatic expressions.
At any rate, the approach that says “Well, Muslims say God is X and we believe God is X, therefore we and Muslims worship the same God” should give anyone pause. Not only is it easy to make dumb analogies like saying that just because your car and my car both have tires doesn’t mean that we’re driving or owning the same car, but this sort of broken theology does a great deal of violence to the very person of Christ and hence the Holy Trinity, and to Islamic theology. Not only do Muslims explicitly deny the Trinity and the divinity of Christ, but what of those attributes that they affirm that we would not, if you’re going to make it all about attributes? If attributes can “make” all gods the same, can they “un-make” him too?
I am reminded of a discussion I got into on this topic here a long time ago. Someone else (I don’t remember who) was trying to explain to me the standard RC line that PRmerger has said about Muslims affirming this and that which we would also affirm as Christians regarding the true God. I asked then, and I would ask again now, that if we should use attributes held in common as a measure of who is worshiping what, then what is to stop me or anyone from inventing a “god” out of whole cloth, selecting those attributes which are most befitting
any description of God (omnipotence, creative power, benevolence perhaps, etc.), and affixing this “god” to any thing I wish? Say I have a Coca-Cola can that I begin to worship for some reason, with prostrations, offerings of sacrifice, etc. I describe this can in terms common to both the OT and NT, as well as the Qur’an. What is stopping this can, this “god”, from being recognized by Catholics who think that it is all about abstract terms (keeping in mind that I have used terms that are specific to their understanding of God) as the true God? After all, there is only one God, so isn’t my can to be recognized as God by virtue of the fact that I am offering sincere worship from my heart to it/him? When I posed this situation to the poster in that old thread, he was incredulous. “That’s silly! It’s not possible for a can to be God! You are affirming true attributes but transferring them to something that is
incapable of being God!”
You don’t say…! 
Now, that is an obvious and stupid example meant to prejudice your reaction in a certain way, but I bring it up again because there’s nothing of the above situation that does not apply directly to Islam, unless you want to argue (which you shouldn’t, as a Christian) that the revelations supposedly received by Muhammad were somehow true and from God, despite the fact that they fall outside of received scripture (you know, the “If anyone should bring another gospel” standard), and directly contradict
our experience of Christ (not just a list of abstract attributes!) in 2,000 years of the Christian Church spread throughout the world. To affirm them anyway would essentially make Muhammad a true prophet, which no Christian in their right mind would agree with. If anything, Islam is all the more insidious because it removes the can (i.e., the part that makes its worship and theology patently ridiculous and transparently wrong) such that
all you’re essentially left with when looking at it is this set of attributes, drawn from the false claims of Muhammad via his false revelation which is the Qur’an. Think about it: The god of the Qur’an/Islam has no son and does not beget, has no form and hence is not incarnate, has no ‘partners’ as Muslims misunderstand the Holy Trinity to be. This god is essentially a monad, existing completely outside of its creation and predestining absolutely what its slaves do. Looked at from this angle, the Allah of Islam has more in common with a child playing with army men than the
pantocrator of Christianity. There’s no real reason to consider them to be even relatable to one another, let alone the same. But I suppose when everything is abstract concepts and adjectives, then anything can be anything. What an odd kind of Christianity or religion in general that is.
