Do Christians and Muslims Worship the Same God?
When this question is asked, it is important to understand not only what someone’s answer is, but what they mean by it. The sense in which a fundamentalist Christian answers the question may not be the same in which a philosophical Catholic answers it – and thus their respective answers may contradict one another even if both are right in what they say.
For example, concerning the controversy surrounding a Wheaton professor’s firing over her (confused) view of Islam, Baylor University’s Francis Beckwith and RZIM’s Nabeel Qureshi came to opposite conclusions. However, these conclusions were arrived at by different means. Beckwith answered primarily by philosophical reasoning (stressing the similarities in classical theology), while Qureshi came from a more religious stance (stressing the differences in biblical/quranic theology).
I would like to offer my take on the issue that I think does justice to both sides, or at least makes clearer why they reach disagreeable conclusions for so many agreeable reasons.
Essential vs. Accidental Attributes
There is a difference between being wrong about a thing and not talking about the same thing. (In fact, in order to be wrong about a thing, one must have that thing thing in mind when one makes the error.) Often errors regarding things are merely “accidental” (in the philosophical sense). So for example, if someone thinks my wife is 7 feet tall, he would be wrong – but he would be wrong about her. Simply getting her height wrong would not mean he is speaking of something other than my wife, because height is an accidental property of a thing. However, if he thought she were a blade of grass, then obviously we are not talking about the same thing, for he has made an “essential” error (i.e., an error regarding her essence).
The problem with answering this question with regard to God (as classically understood) is that He has no accidental properties – he is metaphysically simple (undividable), and so everything true of Him is an essential truth. Thus, there is a sense in which someone saying anything wrong about God cannot be talking about the true God. However, making a mistake about God does not seem to be treated this way in Scripture. Mistakes about God are treated just so – they are not made equivalent to a philosophically sophisticated metaphysical error regarding God’s essence. This is why in the book of Acts, St. Paul could tell pagans that their Unknown God is the one he proclaims as well.
Natural vs. Supernatural Revelation
I think a helpful distinction can be made between natural and supernatural revelation. What can be known of God via creation (“nature”) is more limited than what can be revealed about God by Him telling us things. God does not seem to hold individuals responsible for theological truths that have to be supernaturally revealed until they are revealed. The Jews were certainly not Trinitarian – but they worshiped the God of Abraham just as St. Paul did. This did not change when Jews rejected Jesus’ divinity. They were not treated as if they did not worship the same God Christians did, even as they were judged for rejecting Jesus.
What can be known of God’s attributes via natural revelation (Rom. 1), then, might be a better standard for whether one is referencing the same God. Rather, errors regarding supernaturally-revealed truths might be better classified as heresies – and that is how the Church has treated them (i.e., not as metaphysically essential errors). From nature we know that God is one, that He is creator, etc. – if Muslims denied this (as, say, Mormons do), then a better case could be made that they are not worshiping the same God.
Further, the attributes of God that must be arrived at via deep philosophical reflection ought – as it seems to me at least – to be classified in the same way (as “accidental” rather than “essential” errors) simply because of the difficulty of getting them right. It is one thing to deny the doctrine of God’s singularity, it is another to misunderstand the classical doctrine of divine simplicity (or divine impassibility – one of God’s attributes that is denied by nearly every Christian on the face of the earth today!).
Muslims, then, may be said to worship the same God as Christians do so far as His philosophical (i.e., natural revelation) identification goes due to their acceptance of naturally revealed truths such as that there is only one God that is the creator. Muslims, however, gets God seriously wrong as far as religious (supernatural identification) identification goes due to their rejection of supernaturally revealed truths such as the Trinity and the Incarnation. This is the correct sense in which it is said that Muslims are wrong about God but are not not worshiping another god.
N.B. Practically speaking this amounts to the same problem. Now that God has supernaturally revealed these things, to knowingly reject them places the Muslim (or the Jew or the Mormon or the pagan) not only outside Christian orthodoxy, but outside Christianity.