Glass door between two worlds

The Christian faith is centered on two events which lend Christianity unique appeal, compared to all other world religions: the Incarnation and the Resurrection. At Christmas, we commemorate and celebrate the Creator of the world entering the world he made to redeem it. God passing through the first stages of the human lifecycle. 

At Easter we commemorate and celebrate the hope of immortality, and reunion with departed loved ones. A better life in the world to come, where all tears are wiped away. 

Compare that to a unitarian Christmas: although the messiah has a unique role to play in redemptive history, the person who plays that role is interchangeable with any other human being. There's nothing special about the messiah, just his particular mission. For that matter, Adam, Noah, Abraham et al. each had a unique part to play in redemptive history as well. 

The Incarnation has a two-sided character. There's the physical, this-worldly side of the Incarnation. Then there's the divine, other-worldly side of the Incarnation. Like a door between two worlds. We see the door facing into our world. But on the other side, the door faces into the Godhead. The Incarnation is a glass door through which we see God on the other side.