Do Muslims and Christians Worship the Same God?

The question has been raised and answered in the affirmative in Allah: A Christian Response by Miroslav Volf. In addition to this helpful review, I thought it would be nice to get Calvin's perspective on this issue. The context is Calvin's distinction between the knowledge of God the Creator and the knowledge of God the Redeemer in Christ. At first this distinction might seem to support the notion that adherents of the great monotheistic religions - Judaism, Christianity, Islam - all worship the same Creator God. But in light of Calvin's teaching concerning man's depravity, which has plunged him into spiritual blindness that leads to the creation of false notions of God, i.e., idols, it becomes clear that for Calvin, God cannot be truly known and worshipped even as Creator apart from Christ. He writes:

Christ tells his disciples to believe in him, in order that they might have a distinct and complete belief in God, “Ye believe in God, believe also in me” (John 14:1). For although, properly speaking, faith rises from Christ to the Father, he intimates, that even when it leans on God, it gradually vanishes away, unless he himself interpose to give it solid strength. The majesty of God is too high to be scaled up to by mortals, who creep like worms on the earth. Therefore, the common saying that God is the object of faith (Lactantius, lib. 4 c. 16), requires to be received with some modification. When Christ is called the image of the invisible God (Col 1:15), the expression is not used without cause, but is designed to remind us that we can have no knowledge of our salvation, until we behold God in Christ ... What I wish to impress upon my readers in this way is, that the first step in piety is, to acknowledge that God is a Father, to defend, govern, and cherish us, until he brings us to the eternal inheritance of his kingdom; that hence it is plain, as we lately observed, there is no saving knowledge of God without Christ, and that, consequently, from the beginning of the world Christ was held forth to all the elect as the object of their faith and confidence. In this sense, Irenaeus says, that the Father, who is boundless in himself, is bounded in the Son, because he has accommodated himself to our capacity, lest our minds should be swallowed up by the immensity of his glory (Irenaeus, lib. 4 cap. 8) ... God is comprehended in Christ alone. The saying of John was always true, “whosoever denieth the Son, the same has not the Father” (1 John 2:23). For though in old time there were many who boasted that they worshipped the Supreme Deity, the Maker of heaven and earth, yet as they had no Mediator, it was impossible for them truly to enjoy the mercy of God, so as to feel persuaded that he was their Father. Not holding the head, that is, Christ, their knowledge of God was evanescent; and hence they at length fell away to gross and foul superstitions betraying their ignorance, just as the Turks in the present day, who, though proclaiming, with full throat, that the Creator of heaven and earth is their God, yet by their rejection of Christ, substitute an idol in his place. (Institutes II.vi.4).

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