William B. Yeats (1865-1939)
As a result, things are falling apart disintegrating, and what result from the disintegration is a kind of complete anarchy bringing along with it a lot of bloodshed. The ceremony of innocence (which Yeats valued so much) is the main victim of all this anarchy. The situation is worsened by the fact that the best people are not sure of themselves and their convictions whereas the worst people being very confident are full of passionate intensity.
All these point to the possibility that some revelation i.e., a Second Coming which in its significance is equal to the first coming of Christ, is about to come. Hardly has the poet uttered the words the Second coming than he sees a vision of a vast image emerging out of the racial unconsciousness of mankind. This vision is by no means pleasant as it troubles the sight of the poet.
The vision, the poet sees in that of a shape with a lion body and the head of a man. This shape has a gaze which is as blank and pitiless as the gaze of the sun. Somewhere in the sands of the desert that figure is moving slowly. As it does so, desert birds feel disturbed by the emergence of this unfamiliar figure and the poet in his vision sees their (the desert birds) shadows reeling around this shape. And then suddenly the darkness comes over again i.e., the vision is over. The vision is over but so long as it has lasted it has been able to give the poet the knowledge that when twenty centuries of stony sleep (before the birth of Christ) were disturbed by the rocking cradle of Christ (at Christ's birth) the situation must have been similar to the situation now. The only difference is that in that case it was Christ who was born in Bethlehem and in this case it is rough breast which is moving slowly in slouching style, towards Bethlehem. Its hour has also come round at last i.e., the time for it to herald another era of twenty centuries has come. The big difference of this time is that whereas Christ's influence was all welcome, this is a rough beast and its appearance is more terrifying than welcome. In other words, civilization is for sterner times, at the hands of the new authority which is likely to take over in the wake of this Second Coming.
Sharma, K.N. "The Second Coming by William Butler Yeats: Summary." BachelorandMaster, 23 Nov. 2013, bachelorandmaster.com/britishandamericanpoetry/second-coming.html.