Literary devices enhance the message a poet is trying to convey. Overall, Yeats uses the literary device of ottava rima (eight-line stanzas) with a rhyme scheme of abababcc to carefully structure his poem. Some literary devices that Yeats uses specifically in stanzas four through eight include alliteration, imagery, allusion, apostrophe, and rhetorical questions.
In alliteration, words that begin with the same consonant are placed close together. This puts the emphasis on certain words and adds a pleasing sense of rhythm to a verse. Some examples of alliteration in these stanzas are "finger fashion" in stanza four, "Fingered upon a fiddle-stick" in stanza six, and in stanza eight, the repeated "b" sounds in:
The body is not bruised to pleasure soul,
Nor beauty born out of its own despair,
Nor blear-eyed wisdom.
Imagery is description using the five senses of sight, sound, taste, smell, and touch. Some examples are "hollow of cheek," "youthful mother," and "old clothes upon old sticks to scare a bird." All of these are visual images we can picture with our mind's eye.
The poem is full of allusions, which are references to other literature or to events or people outside the poem. Yeats' speaker refers both to his beloved, Maud Gonne, now aged, and Leda, the beautiful swan raped by Zeus when he alludes to "pretty plumage once." The speaker also alludes to three Greek philosophers with very different views of life in stanza six: Plato, who was more interested in ideals that worldly reality, Aristotle, who was a realist, and Pythagoras, who found beauty in what he believed was the music of spheres.
Apostrophe is addressing an inanimate object or person who is absent. Yeats, uses this device in stanza eight when he addresses the chesnut tree: "O chestnut tree ..." You can find other places that begin with "O," which are examples of apostrophe. Directly addressing an object brings a sense of immediacy or urgency.
Finally, Yeats ends the poem with rhetorical questions, such as the famous "How can we know the dancer from the dance?" The point the speaker is making is that we are known by what we do, and the two can't be separated. We are also known as the sum of our parts, as when the chestnut tree is asked: "Are you the leaf, the blossom or the bole?" Of course, it is all of these together.