Christianity has a historical founder whose existence is verified by outside sources. The most reliable of these sources is the account from Josephus, a first-century Jewish historian born in Jerusalem, who eventually became a Roman citizen. In his work, Antiquities of the Jews, he makes several brief references to Jesus, both as a Messiah and as a wise teacher. Josephus also records that Jesus was crucified, and that his followers believed he was restored to life. Beyond that, however, history is silent.
First and foremost, Christians believe that Jesus is both fully human and fully divine: the technical formula is “one person, two natures.” Christians believe Jesus was neither just another enlightened teacher on the one hand, nor a divine avatar on the other—God in a human disguise. Instead, in all his words and deeds, Jesus was both fully and completely divine and also a real, embodied human being. The language Christians use to describe this is “incarnation.” That is, Christians believe God became “incarnate”—literally, “in-fleshed”—in one human being, Jesus of Nazareth, son of a young woman named Mary, and her husband, Joseph.
Second, in Jesus, Christians believe they have the clearest expression of God’s core nature, and how God wants to be in relationship with humanity and the world. This is why Jesus’ life—his ministry, his friends, his disciples—all are crucial to a Christian understanding of God. Christians believe that the fundamental disposition of God toward creation is love, and that everything God does in the world is meant to manifest that love. In his person and in every act of his human life, Jesus is thought to embody that love.
Another point needs to be mentioned here as it relates to Jesus’ life and ministry, and that is that Jesus was very transgressive, repeatedly violating social norms and “queering” traditional notions of power and social status. He did not align himself with the Pharisees, the Jewish authorities of the time; indeed, they received regular and repeated chastising from Jesus for their emphasis on rules over people. Instead, Jesus surrounded himself with tax collectors, prostitutes, and other questionable members of society, welcoming children onto his lap, healing lepers, and conversing with strange women. Over and over again, Jesus aligned himself with outsiders: with the poor and the polluted, the underprivileged, and the unwanted.