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 speaker opens the poem with these lines, in which they offer a series of images that announce the collapse of the current world order. Several things are worth noting about these lines. First, they form a quatrain organized by a loose AABB rhyme scheme. Though the rhymes are inexact, they are among the only rhymes in the entire poem, which makes them significant. Second, it’s noteworthy that the speaker uses the passive voice in the fourth line. When they say, “Mere anarchy is loosed upon the world,” they emphasize the lack of control in the face of overwhelming chaos. Instead of being able to act, “the world” is acted upon. Yeats subtly echoes this powerlessness on the level of meter, and particularly in the opening line: “Turn-ing / and turn- / ing in / the wid- / en-ing gyre.” The image here is one of spinning and disorientation, which Yeats echoes in the meter, which changes from one foot to the next. Finally, the phrase “widening gyre” references Yeats’s mystical theory of history, which he illustrated through a diagram made of two spirals. These spirals spin in contrary directions, organizing history into two-thousand-year cycles separated by periods of cataclysmic transformation.

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

Lines 9–13 open the second stanza, where the speaker turns from describing present conditions to their prophecy of the future. These lines feature a lot of repetition, which has an ambiguous effect. The speaker repeatedly insists that “the Second coming is at hand,” a claim they qualify, twice, with the adverb “surely.” Despite the insistence, it’s possible that they are using repetition to convince the reader—and indeed themself—of what they’re saying. That said, it’s worth noting that Yeats constructed these lines in such a way the verb “is” consistently occupies an accented position:

     Sure-ly / some rev- / el-a- / tion is / at hand;
     Sure-ly / the Se- / cond Com- / ing is / at hand.

The repeated emphasis on is goes some way to reflect the speaker’s confidence. Furthermore, the identical rhyme between “hand” and “hand” communicates a sense of certainty that prepares the way for what comes next: the speaker’s prophecy. They introduce this prophecy by explaining how “a vast image” came to them from what they call “Spiritus Mundi.” This is a Latin phrase that literally translates to “spirit of the world” or “world spirit.” In the metaphysical system Yeats developed, this world spirit is an immense intelligence that unites everyone in the world—albeit on a metaphysical plane.

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?

The speaker closes the poem with these lines (18–22), which come after they have described a sphinx-like creature with a human head and the body of a lion. In the twilit vision that closes their prophecy, the speaker notes that this “rough beast” has risen from the desert after two thousand years of “stony sleep.” It has woken up as a result of being “vexed to nightmare by a rocking cradle.” This line references the cradle of the infant Christ, which the speaker clarifies two lines later, when they envision the beast traveling to the place of Christ’s birth: Bethlehem. The implication here seems to be that the rough beast will replace Christ as the dominant spiritual figurehead, thereby inaugurating a new historical world order. Yet the closing lines are full of ambiguity. This ambiguity is most clearly signaled by the fact that the speaker concludes the poem with a question. However much they may have seen of the “rough beast” in their vision, they don’t really know what this creature’s arrival will bring. It remains an enigma, and hence a symbol for the terror of the unknown.