He is also saying that the birth of Christ in Bethlehem was a nightmare for the world it altered, the world that it changed utterly a change that Yeats sees as the end now of the Christian Era and not its fulfillment.

他还说,基督在伯利恒的诞生,是一个噩梦，因为世界因此改变，彻底变了,叶芝把这个改变,看作基督时代的终结,而不是它的圆满。

耶鲁公开课 - 现代诗歌课程节选