The Second Coming

- by W.B. Yeats

Turning and turning in the widening gyre
The falcon cannot hear the falconer;
Things fall apart; the centre cannot hold;
Mere anarchy is loosed upon the world,
The blood-dimmed tide is loosed, and everywhere
The ceremony of innocence is drowned;
The best lack all conviction, while the worst
Are full of passionate intensity.
Surely some revelation is at hand;
Surely the Second Coming is at hand.
The Second Coming! Hardly are those words out
When a vast image out of Spiritus Mundi
Troubles my sight: somewhere in the sands of the desert
A shape with lion body and the head of a man,
A gaze blank and pitiless as the sun,
Is moving its slow thighs, while all about it
Reel shadows of the indignant desert birds.
The darkness drops again; but now I know
That twenty centuries of stony sleep
were vexed to nightmare by a rocking cradle,
And what rough beast, its hour come round at last,
Slouches towards Bethlehem to be born?

 

Yeats' believed in the dual nature of existence & the "Gyre." 

More about the philosophy here & here.

[I]f each gyre is depicted as a single principle, then the gyre moves from the total preponderance of one principle over the other, through increasing admixture of the second principle to equality at the point where the surfaces cross each other, until the minimum of the first and the maximum of the second principle are reached. At this point the reflux starts, so that there is never more than a momentary predominance of either principle, and the system is constant movement.