It’s frequently said that Christians and Muslims worship the same God.

One can even find this statement in official documents of various Christian churches and denominations. For instance, in the Second Vatican Council document Nostra Aetate, the Roman Catholic Church writes:

“The Church regards with esteem also the Moslems. They adore the one God, living and subsisting in Himself; merciful and all-powerful, the Creator of heaven and earth, who has spoken to men; they take pains to submit wholeheartedly to even His inscrutable decrees, just as Abraham, with whom the faith of Islam takes pleasure in linking itself, submitted to God.”

Statements such as these are usually intended as reminders that Christians and Muslims share some beliefs in common; that it’s not all stark difference.

But are these kinds of statements really true? After all, as many assert, Christians and Muslims do have some significantly divergent beliefs about this supposedly-same God they worship. It’s central to the Christian faith to believe that Jesus Christ is God, that he died to save humanity from their sins, and that he rose from the dead to complete this salvation. Muslims believe none of this. Christians believe Jesus Christ is the fullness of revelation, and that this revelation is communicated through the Bible. Muslims believe the fullness of revelation is contained in the Qur’an, communicated by God to Mohammed through the archangel Gabriel. Christians see Muslim terrorists today committing violent actions in the name of the Qur’an, and see no such violence condoned by the New Testament.  

So, can it still be meaningfully said that Christians and Muslims worship the same God?

According to philosophy professor Edward Feser—an expert in the thought of Thomas Aquinas—the answer is “yes”.

In a popular blog post last December, he explained why.

“First,” he writes, “we need to keep in mind the Fregean point that a difference in sense does not entail a difference in reference”:

“To use [Gottlob] Frege’s famous example, the sense of the expression ‘the morning star’ is different from the sense of the expression ‘the evening star.’ But those two expressions refer to one and the same thing, viz. the planet Venus. Similarly, expressions like ‘the God of the Christians’ and ‘the God of the Muslims’ differ in sense, but it doesn’t follow from that alone that they don’t refer to the same God. By the same token, though the expression ‘God’ is different from the expression ‘Allah,’ it doesn’t follow that God is not Allah, any more than Stan Lee and Stanley Martin Lieber are different men.”

“Second,” writes Feser, “even a speaker’s erroneous beliefs don’t entail that he is not referring to the same thing that speakers with correct beliefs are referring to”:

“Consider an example made famous by Keith Donnellan. Suppose you’re at a party and see a man across the room drinking from a martini glass. You say something like ‘The guy drinking a martini is well-dressed.’ Suppose, however, that the man is not in fact drinking a martini, but only water. It doesn’t follow that you haven’t really referred to him. Furthermore, suppose there is a second man, somewhere in the room but unseen by you, who really is drinking a martini and that he is dressed shabbily. It doesn’t follow that you were, after all, really referring to this second man and saying something false. Rather, assuming that the first man really is well-dressed, you were referring to that first man and saying something true about him, even though you were wrong about what he is drinking. And thus you are referring to the very same man as people who know that he is drinking water would be referring to if they said ‘The guy drinking water from a martini glass is well-dressed.’ Similarly, the fact that Muslims have what Christians regard as a number of erroneous beliefs about God does not by itself entail that Muslims and Christians are not referring to the same thing when they use the expression ‘God.’”

As Feser admits, not everything goes. Someone’s beliefs about “the one God” could be so far off that he could not be meaningfully said to worship the same God as Christians. But Feser doesn’t think this is the case between Christians and Muslims.  

No matter what one thinks about Feser’s arguments, it should be said that his and others’ support for the claim that Christians and Muslims worship the same God need not imply a form of tolerance that whitewashes differences. There are some very important differences between Christians and Muslims that should be (civilly) discussed and debated.

But it is perhaps because these differences refer to the same God that discussion and debate is even possible.