The poem `The Second Coming`by William Butler Yeats invokes both traditional Christian iconography and a mystical account of the world set forth by Yeats himself in his book A Vision, which identifies the world as existing in a set of recurring cycles, called gyres.
The notion of a second coming in traditional Christianity is take from Revelation, and presumes that at some point in the future, Jesus Christ will return to the world to judge both the living and the dead. This return will be preceded by an apocalyptic period in which various disasters are unleashed upon the world, including the four beasts. Many of the prophesies in Revelation are set in the environment of the Holy Land, and represent a return of Jesus for his second coming to the place of his first incarnation.
Although the chronology and setting are Christian, and the sense of millenial ending typical of the fin de siecle, and the condemnation of moderrnity also shared with many of the poets of the period:
The best lack all conviction, while the worst
Are full of passionate intensity. ...
and the notion of anarchy having replaced Christianity as the centre of the world are shared by poets from Matthem Arnold (caught between two worlds, one dying and one unable to be born) and T. S. Eliot.
Yeats wrote "The Second Coming" in 1919, in the wake of the cataclysm that was World War I. Additionally, Ireland, his homeland, was in the midst of a violent uprising against British rule, and the Bolshevik Revolution rocked Russia. This turmoil seemed to confirm a notion that scholars observe Yeats had held for some time—that world history was essentially cyclical. This theme is expressed in the image of the falcon, which is spiraling beyond the control of the falconer. Yeats suggested, in a haunting and evocative way, that the two-thousand year era of Christianity was coming to an end, ushering in a new era. This millenarian, apocalyptic vision is another major theme of the poem. But Yeats does not envision the arrival of a new two thousand year era of peace, rather darkly imagining a "rough beast . . . [that] slouches toward Bethlehem to be born." The end of the Christian era evokes the possibility of a new era of barbarism and possibly human misery and degradation. This pessimism, shared by many of Yeats's contemporaries, is another important theme of the poem.