In the interlude, Becket gives a sermon on Christmas morning at Canterbury Cathedral, six days after he’s arrived in Canterbury. He explains that there is a deep mystery behind Christmas Day—that celebrating the birth of Christ also means remembering his death, such that one must both rejoice and mourn at the same time. Becket says that, from an ordinary, worldly (vs. divine) perspective, this mixture of rejoicing and mourning can appear to be strange, and that Christian experience is unique for having such mysteries at its heart.
Becket emphasizes the distinction between worldly and spiritual perception by noting the simultaneous rejoicing and mourning characteristic of celebrating Christmas. Whereas the worldly view is dualistic, seeing the two as absolutely separate, the unique mystery of Christianity is that the two can somehow be considered together when contemplating Christ.
Becket then asks his audience to consider what ‘peace’ means. He draws a contrast between a worldly conception of peace and a divine one, asking the congregation to remember that the peace which Jesus said he gave to his disciples was “not as the world gives.” Jesus’s disciples, he points out, knew no such thing as worldly peace—they were constantly facing hardships and pain.
Becket continues to emphasize the distinction between worldliness and spirituality. Jesus promised a peace that was not sourced in the world—and this is demonstrated by the fact that his disciples suffered immensely. The divine peace offered by Jesus is beyond the bounds of worldly thinking.
Becket turns the congregation’s attention to the concept of martyrdom, noting that, the day after Christmas, the Church celebrates the martyrdom of Stephen, the Lord’s first martyr. He says that celebrating Stephen’s martyrdom involves the same mixture of rejoicing and mourning as the celebration of Christ’s birth. He emphasizes that martyrs shouldn’t be thought of simply as good Christians who’ve been murdered for being Christians, for this would only involve mourning; nor should they be thought of as good Christians who’ve been raised to the status of sainthood, since this would only involve rejoicing, “and neither our mourning nor our rejoicing is as the world’s is.” Further, he emphasizes that martyrs are “made by the design of God,” and that martyrdom is not something brought about by the human will or conscious intention. Martyrdom involves total submission to the will of God.
Becket wants the congregation to think about martyrdom from a more divine perspective, to view it in a way that defies everyday, worldly thinking about the human will. Becket says that martyrs do not choose their martyrdom; their death, rather, is a part of God’s design—they are instruments of a divine will, a will to which they’ve wholly submitted. Because of the complexity of martyrdom—of the paradox it causes for thought (as the martyr both submits to God and is simultaneously submitted by God’s plan)—the way we celebrate them must match that complexity, and thinking dualistically about mourning and rejoicing fails to do that.
Becket ends his sermon by telling his congregation that he doesn’t think he will ever preach to them again. He says that, in not too long a time, they may have another martyr.
Becket boldly alludes to the fact that he is pursuing martyrdom himself, foreshadowing his death in the second part of the play.