You can find a loving conception of monotheism in both Judaism and Islam, but only in Christianity does this love manifest itself in a one-way work of salvation of sinners apart from religious effort. For this reason, C.S. Lewis has famously said of Christian faith, "We trust not because ‘a God’ exists, but because this God exists.”
There are of course many Jews, Muslims, and Christians who believe all three faiths worship the same God, but through different expressions. We see this view suggested even in the Muslim’s Koran:
Do not dispute other than in a good way with the people of Scripture, except for those of them who do evil; and say: “We have faith in that which has been revealed to us and revealed to you. Our God and your God are One, and to Him we submit [ourselves].” (Surah 29:46)
Jews and Christians, also, have so much good theology in common. It has become common among people in both faiths to refer to “Judeo-Christian values.” This is a real thing, and in many cases, a completely legitimate expression. In a 2007 interview, then-President George W. Bush said this: “I believe in an almighty God, and I believe that all the world, whether they be Muslim, Christian, or any other religion, prays to the same God. That's what I believe.”
This belief is practically mainstream within all three of those faith traditions. But I think we come at this answer too easily, too thoughtlessly, simply assuming that because these three religions—Judaism, Christianity, and Islam—are all monotheistic and share some historical heritage, they must worship the same God. Because lots of people worshiping one God does not mean they are worshiping the same God.
Do Jews and Christians worship the same God?
This is a very complex question, actually, but the short answer is: no.
You may of course flinch at such an assertion. It is not a necessarily popular belief, even within evangelical Christianity, where many simply believe Jews worship what they know of God. It is said that they worship the one true God, but simply have an incomplete vision of him. But couldn’t this be said of any religious faith whose object of worship bears striking similarities with the God that Christians worship?
Complicating the question are the various threads within both Judaism and Christianity. One Jewish scholar has said, “The fact is that there is no single Jewish understanding of God.” This makes it difficult to distinguish Christianity from Judaism, if only because we aren’t dealing with Judaism so much as Judaisms. On the other hand, Christianity has remained almost entirely unified for two thousand years on the central matters of its theological claims. But one stark contrast between the Christian view of God and the Jewish view is on this thing called grace.
Now, drawing the line at the concept of grace may seem too narrow a division. The God revealed in the Jewish Tahakh displays abundant grace constantly. Christians would affirm that. But we also believe that we must believe about God what God has revealed about himself, and in fact that to disbelieve what God has revealed about himself and to worship some version of God we prefer is in fact to worship an idol. In the historic account of the children of Israel worshiping the golden calf, in fact, we see that Aaron and the Israelites attributed their worship of this false god to God (Exodus 32:5).
When Christians talk about grace, however, the thing that makes Christianity utterly unique among all faiths, we aren’t simply referring to a disposition of God or a personality trait. We are referring to those things too, of course, but more specifically, we are referring to the way God has expressed his grace, namely through the person and work of Jesus Christ.
It is at Jesus, in fact, that Judaism and Christianity part theological ways.
This is not simply a matter of opinion. It is a matter of diametrically opposed truth claims. And we see this opposition recurring over and over again throughout the teaching ministry of Jesus depicted in the Gospels of the New Testament.
In John chapter 8, the orthodox Jewish leaders are once again spying on Jesus, trying to trip him up, expose him, defame him, and shame him. You have to understand that the Pharisees of Jesus’ day were not fringe characters in the Jewish religion. They were the religious elite, of course, but theologically speaking, the represented mainstream, “contemporary” Judaism. They shared much of the same theology as Jesus and his disciples. The Pharisees represented the faithful reading of the Hebrew Scriptures. They believed in the covenantal history, in a future resurrection, and in applying the revelation of God to everyday life. They would be the equivalent, probably, of the fundamentalist strain of Christianity today—culturally zealous and a little rough around the edges, but on all the majors, pretty much theologically correct.
So it is no little thing that Jesus and the Pharisees butt heads here in John 8. This is not simply a clash between nice Jesus and mean leaders. It is much more than that. It is a fundamental disagreement on the very identity of God.
Jesus is doing what Jesus always does: making everything about himself. In this instance, he claims to be the Judge, the Light of the World, the way to freedom from sin, and a few other equally provocative things. This is not the kind of thing a normal religious leader says. We don’t tend to take seriously religious leaders who make such claims about themselves.
Jesus then says something even stranger:
Your father Abraham rejoiced that he would see my day. He saw it and was glad.” So the Jews said to him, “You are not yet fifty years old, and have you seen Abraham?” Jesus said to them, “Truly, truly, I say to you, before Abraham was, I am.” (John 8:56-58)
What does he mean?
Jesus is saying two incredible things here. First, he claims to be in existence before Abraham. This is an overt claim to preexistence, in fact to eternality and omnipresence. And by saying “I am”—asserting that thousands of years ago, not only was he, but he currently is—he is applying the sacred name of Yahweh (“I AM”) to himself. This may sound subtle, but it’s not subtle at all. Jesus is in fact claiming to be God. We know the orthodox Jews understood him to be making this claim, because the very next thing they do (John 8:59) is pick up stones to kill him, which is exactly what a good Jew would feel inclined to do when confronted with such blatant blasphemy.
Again, this is not merely a matter of opinion. This is not simply a case of the Jewish theologians worshiping the same God in a different way. If Jesus is in fact God, and you try to kill him, how could we say in any legitimate way that you worship and believe in God?
Jesus makes this very point, actually, in the same chapter.
Jesus said to them, “If you were Abraham's children, you would be doing the works Abraham did, but now you seek to kill me, a man who has told you the truth that I heard from God. This is not what Abraham did. You are doing the works your father did.” They said to him, “We were not born of sexual immorality. We have one Father—even God.” Jesus said to them, “If God were your Father, you would love me, for I came from God and I am here. I came not of my own accord, but he sent me. Why do you not understand what I say? It is because you cannot bear to hear my word. You are of your father the devil, and your will is to do your father's desires. He was a murderer from the beginning, and does not stand in the truth, because there is no truth in him. When he lies, he speaks out of his own character, for he is a liar and the father of lies. But because I tell the truth, you do not believe me. Which one of you convicts me of sin? If I tell the truth, why do you not believe me? Whoever is of God hears the words of God. The reason why you do not hear them is that you are not of God.” (John 8:39-47)
To summarize, Jesus is saying that if somebody worshiped the true God, they would worship him, because he is of the same nature of the true God. And he is saying that if anyone rejects him, they reject the one true God. And further, he is saying, that if anyone—including these orthodox Jews—do not believe in him, they are more aligned with the enemy of God, Satan himself.
I share that lengthy passage above so you will see that I am not making this up. Jesus said it. And you are welcome to disagree, and you are welcome to be offended. But you should plainly see that Jesus is himself saying that to reject him is to reject God, deny the truth, and reveal oneself as being “not of God.”
In John chapter 10, verse 30, Jesus doubles down on these claims, and says, “I and the Father are one.” Once again, the Jewish theologians take up stones to murder him, which they would not have done if all he meant was that he and God were “on the same team.” John 10:33 makes their motive explicit:
The Jews answered him, “It is not for a good work that we are going to stone you but for blasphemy, because you, being a man, make yourself God.”
I believe it is very important that we understand this important contrast if we want to understand both orthodox Christianity and the orthodox Judaism that develops from the time of Christ onward. The conflict between Jesus and the unbelieving Jews of his day did not rise or fall on how nice Jesus was compared to how mean the Pharisees were. That’s a very superficial reading of Jesus’ relationship with the religious leaders, which is probably why it’s the most common understanding in the secular world of why Jesus was killed.
But while Jesus was a faithful and religious Jew, his beef with the Pharisees and scribes was not simply some intramural personality clash. It was a fundamental clash of worldviews. Namely, Jesus was orienting the world around himself, putting himself in the center of everything. He was in fact claiming to be God. And if he was right—as I believe he was—then to disagree with him was to disagree with God. To deny him was to deny God. To reject him was to reject God. And to worship someone at the exclusion of Jesus, is to worship another god.
Christians believe that God became flesh in the person of Jesus Christ, who was conceived by the Holy Spirit in the womb of a virgin named Mary and grew and developed into mature, real, tangible manhood.
So, do Jews worship the same God as Christians? The Christian faith has its roots in the Jewish culture and religion, and the two faith traditions share a common sacred history, but as it really counts—meaning, as it really applies to a relationship with the supreme deity who actually exists—the answer is no. Because if God has revealed himself in Jesus Christ, if indeed Jesus Christ is God, if indeed God is a Trinity, then to reject these truths about his very nature—which is not the same as being mistaken about certain attributes of God or not understanding certain aspects of his personality—means rejecting God himself.
Jesus Christ makes all the difference in the world.
This post is an adapted excerpt from Unparalleled: How Christianity's Uniqueness Makes it Compelling by Jared C. Wilson, forthcoming from Baker Books
 C.S. Lewis, “On Obstinacy in Belief,” in “The World’s Last Night” and Other Essays (San Diego: Harcourt, 1988), 25.
 Mona Moussly, “Bush denies he is an ‘enemy of Islam’,” Al Arabiya News (October 5, 2007)
 Alon Goshen-Gottstein, “God Between Christians and Jews—Is it the Same God?” (pdf) Paper presented at the Yale Center for Faith and Culture