The first of the three books into which the work is divided (on Sacrifice in general) gives us the general context of the whole; nothing need be said about it here. But for the second book a note is necessary. The discovery that nearly a quarter of the work concerns the mystery of the Incarnation may be at first a little startling. The explanation is two-fold. First is the author's most legitimate desire to show us the Mass as the very centre of Christianity, the focal point of our entire religion. The Incarnation leads up to it, explains it and is itself further explained by it.