Lines 12-17: These lines are an example of symbolism, and they contain several symbols that can really be disconnected from another. In general, they represent a confused "veiled" vision of the "rough beast" described later in the poem. They are said to originate in Spiritus Mundi, a "spirit world" of images and symbols that Yeats believed to have been traditionally available to the most perceptive people (like poets) throughout history. Although lots of smart-sounding people like to say that symbols always have to "mean" something specific, Yeats thought that the best symbols couldn’t ever be fully explained in words. They are "expressive" in a way that passes beyond ordinary speech.