Speaker or Narrator, and Point of View
The poem is written in the first person (though the speaker only mentions himself once)
Form and Meter
The poem is written in a very loose iambic pentameter, though it resembles free verse more in places
Metaphors and Similes
The falcon and the falconer are each metaphors, representing humanity and a controlling, prevailing force that sets humans on a specific path. The "blood-dimmed tide" is a metaphor for waves of violence, and the "ceremony" of innocence is a metaphor for the entirety of human innocence and goodness. The "rough beast" is also a metaphor: for the mysterious, rapidly approaching Second Coming.
Alliteration and Assonance
The poem begins with the words "turning and turning," and the repetition immediately conjures up a sense of reverberation and mirroring that echoes throughout the poem. The first three lines and the fifth through seventh lines all begin with T, and this use of alliteration adding to a sense of repetitiveness. The word "loosed" is repeated twice in the fourth and fifth line, and "surely" and the phrase "The Second Coming" are repeated in the start of the second section, each respectively examples of alliteration. Then there's "falcon/falconer/fall" and "center cannot," as well as "darkness drops" and "stony sleep" in the second section, which are also examples of alliteration. Together these pairs of repeated consonants create the poem's almost lyrical, singsong feel, adding to its sense of unease and its riddle-like tone.
Irony
The phrase "the best lack all conviction, while the worst / Are full of passionate intensity" is an example of irony because it is ironic, almost bleakly absurd, that the worst people are the most passionate and the best are the least determined to make their voices heard in Yeats's apocalyptic poem-universe.
Genre
Setting
The widening gyre (all of existence?) and a dreamlike desert
Tone
Ominous, prophetic, eerie, unnerved, foreboding
Protagonist and Antagonist
The poem's clearest protagonist is its speaker, who has a mind discerning enough to realize what is happening. The antagonist is the "rough beast" and all the chaos and violence it brings along with it.
Major Conflict
This poem is fundamentally about conflict—the conflict between good and evil, between the past and the future, between tradition and rebellion, between freedom and control. It is about a conflict between Christianity and pre-Christian pagan and occult ideas, and about conflicts between nations and political factions that were occurring at the time, like the Bolshevik Revolution and the Irish War Of Independence. It is also about the nature of conflict itself, which tears apart and destroys established patterns of meaning, reason, and ways of life.
Climax
The poem's climax is certainly its conclusion, at which a "rough beast" is "slouching towards Bethlehem to be born." These ominous last lines give a shape and image to the oncoming crisis, which before this was only a nebulous, faceless idea. By personifying the coming destruction, Yeats endows it with feet and determination. He associates the Second Coming with the ancient, primal human fear of beasts lurking in the dark during our days as cavemen, which helps the poem create its truly terrifying atmosphere.
Foreshadowing
The entire poem is foreshadowing the coming of something, from its start to its finish. The poem even involves literal shadows—the shadows of "indignant birds"—but part of what makes the poem so unnerving is that it never tells us exactly what it is foreshadowing. Instead, it shows is the looming shadow of something rapidly approaching, something that will tear down the walls of all we have ever known.
Understatement
Saying that the image of the sphinx and birds in the desert merely "troubles [his] sight" is an understatement on the narrator's part, expressing only a fraction of the fear he must be feeling about this foreboding prophecy of the future.
Allusions
The Spiritus Mundi is an allusion to a Latin phrase meaning world-soul.
Metonymy and Synecdoche
Personification
The apocalypse or collapse of order is personified as a "rough beast"
Hyperbole
The phrase "surely the Second Coming is at hand" is a bit of an exaggeration—even though the world was in turmoil when Yeats was writing this poem, saying that "surely" a Biblical-scale apocalypse is approaching, without a fraction of doubt, is an example of hyperbole.