I was once at a conference, talking with some colleagues who had a display at a hotel. A Muslim man approached us, demanding that one of us—just one of us—answer just one question, something no one had ever been able to answer for him. “You say that Jesus is God, right?” I answered in the affirmative. “And you say that God is in heaven, right?” I nodded. “And you say there is only one God, not two?” I smiled, knowing where he was going. “Then how is it,” he said, pointing his finger at me, “that God was talking to God?! It makes no sense at all!”

I asked him if I could ask him a question: “Are you a human being?” Yes, he replied. “Am I a human being?” He nodded. “We are both human but we are not the same person. So the Father and the Son share the same nature of God but are distinct persons.” He unleashed a string of expletives and walked away.

Now my reply was not fully adequate, and the analogy has some severe limitations (as Bob Letham explains in his excellent book on The Holy Trinity), but it at least tries to start the conversation with a distinction between nature and person (which I’ve briefly written about here).

So does the New Testament really teach that Jesus is God? The NT often uses “God” (Greek: theos) as synonymous with “God the Father”— and Jesus is not the Father. But the NT also frequently uses “God” as the more generic term for the divine nature. So “God” is not always a reference to the Son in particular, but the Son is always God.

There are several examples where Jesus is explicitly called God. Here are the clearest ones:

John 1:1, “In the beginning was the Word, and the Word was with God, and the Word was God.”

John 1:18, “No one has ever seen God; the only God, who is at the Father’s side, he has made him known.”
John 20:28,  ”Thomas answered him, ‘My Lord and my God!'”
Romans 9:5,  ”To them belong the patriarchs, and from their race, according to the flesh, is the Christ who is God over all, blessed forever. Amen.”
Titus 2:13, “waiting for our blessed hope, the appearing of the glory of our great God and Savior Jesus Christ”
Hebrews 1:8,  ”But of the Son he says, ‘Your throne, O God, is forever and ever, the scepter of uprightness is the scepter of your kingdom.'”
2 Peter 1:1,  ”To those who have obtained a faith of equal standing with ours by the righteousness of our God and Savior Jesus Christ”

But the evidence for Jesus’ divinity is hardly limited to these examples where he is explicitly identified as God. Murray Harris, who wrote a definitive treatment on this question (Jesus as God: The New Testament Use of Theos in Reference to Jesus) has a helpful summary of the broader lines of evidence:

Even if the early Church had never applied the title [‘God’] to Jesus, his deity would still be apparent in his being

the object of human and angelic worship and of saving faith;

the exerciser of exclusively divine functions such as creatorial agency, the forgiveness of sins, and the final judgment;

the addressee in petitionary prayer;

the possessor of all divine attributes;

the bearer of numerous titles used of Yahweh in the Old Testament; and

the co-author of divine blessing.

Faith in the deity of Christ does not rest on the evidence or validity of a series of ‘proof-texts’ in which Jesus may receive the title θεός but on the general testimony of the New Testament corroborated at the bar of personal experience.

Murray J. Harris, “Titus 2:13 and the Deity of Christ,” in Pauline Studies: Essays Presented to F. F. Bruce, ed. Donald A. Hagner and Murray J. Harris (Grand Rapids: Eerdmans, 1980), 271.

An excellent book that lays out all of the evidence—going beyond just the New Testament to include the Old Testament, the history of the church, the place of contemporary culture, and the role of missions, is The Deity of Christ, part of the Theology in Community series edited by Christopher Morgan and Robert Peterson.
One of the most accessible books on this topic is Robert Bowman and Ed Komoszewski’s Putting Jesus in His Place: The Case for the Deity of Christ. They provide a helpful way to remember the case for Christ’s divinity through the acronym H.A.N.D.S. 
  • Jesus deserves the Honors only due to God,
  • Jesus shares the Attributes that only God can possess,
  • Jesus is given Names that can only be given to God,
  • Jesus performs Deeds that only God can perform
  • Jesus possesses a Seat on the throne of God

Finally, it’s worth remember the helpful summary of Jaroslav Pelikan:

The oldest surviving sermon of the Christian church after the New Testament opened with the words: “Brethren, we ought so to think of Jesus Christ as of God, as the judge of living and dead. And we ought not to belittle our salvation; for when we belittle him, we expect also to receive little.”

The oldest surviving account of the death of a Christian martyr contained the declaration: “It will be impossible for us to forsake Christ . . . or to worship any other. For him, being the Son of God, we adore, but the martyrs . . . we cherish.”

The oldest surviving pagan report about the church described Christians as gathering before sunrise and “singing a hymn to Christ as to [a] god.”

The oldest surviving liturgical prayer of the church was a prayer addressed to Christ: “Our Lord, come!”

Clearly it was the message of what the church believed and taught that “God” was an appropriate name for Jesus Christ.

—Jaroslav Pelikan, The Christian Tradition: A History of the Development of Doctrine, Vol. 1: The Emergence of the Catholic Tradition (100-600) (Chicago: University of Chicago Press, 1971), p. 173; emphasis added.