And I recall that, rather late in his life and for one more time, Rev. Schillebeeckx insisted to an interviewer that in the theological field of Christology, it was the BIRTH of Jesus that is the core, the central event, of the Christian faith, and that Easter would never have been possible without it!  Somehow, Catholicism (and most all of Christian churches) switched the two many centuries ago, so that we have been left with liturgical confusion.  Christmas is the start of our Journey to the Cross.