One central mystery of church doctrine, Incarnation, reconciles the humanity and the divinity of Christ. Another, the Trinity, reconciles the divinity of Christ with the divinity of God. To early theologians Jesus of Nazareth was clearly different from the "father" in heaven whom he mentions or addresses often. But he was also divine, and in a monotheistic religion he must therefore be identical with the invisible God in heaven. This contradiction exercised the best minds of the early Christian church, and it doubtless troubles many believers still.