Do Muslims and Christians worship the same God?
It seems to me that when the relationship between Islam and Christianity is engaged on this level, theologians of a more liberal bent are provided a delicious opportunity to flatten the antithesis between Christ and Allah.
The question so framed allows for subtleties in metaphysics to rise to the fore. “Isn’t there only one, real God?” they ask, finger raised. “And if there is only one, real God, then it follows that worship must be directed, even if somewhat confused, to this one, real God. Thus, it should be plain, dear friend, that we are worshiping the same God.”
Well, it isn’t all that plain. But that isn’t the point. The problem here is the desire to build upon perceived ambiguities so as to construct a viewpoint that downplays key differences between Islam and Christianity.
Those of a more liberal mindset don’t want hard edges. They want Muslims to go to heaven as Muslims. This, it seems to me, is the impetus behind the question.
So let’s not start there. Let’s ask other, more relevant questions; the kind of questions that readily dispel ambiguities:
Did Mohammad communicate to humanity revelations from God? No.
Is Mohammad a false prophet? Yes.
Would Christ condemn Mohammad? Yes.
Did Mohammad preach a false gospel? Yes.
Did Mohammad have a high enough view of Christ? No.
Did Mohammad deny the death, burial and resurrection of Christ? Yes.
Did Mohammad accurately portray God? No.
Would Paul, Peter, or any of the other apostles have had anything especially good to say about Mohammad if they could have been made aware of his life and teachings? No way.
If we can attain clarity about these questions, the issue of worship ought to be much easier to navigate. For even if we grant that Muslims direct their worship to the only true God, we will be compelled to say that it is worship offered in vain. God is not pleased with it, and it doesn’t help their situation. They need to accept the Gospel of Jesus Christ.
No amount of placating or theological redefinition can change this fact. So why muddy the waters? One might as well get to the nub of the issue.
For a recent dialogue on this subject, I would point you to the following episode of Unbelievable.
 Which isn’t to say that one ought to be pugnacious or overbearing in their evangelism to Muslims. But it does mean that both sides ought to fully acknowledge what is at stake without watering the issue down.