The wandering of the waters mimics that of the serpent, but it’s not “error” in a bad way – this is before the Fall, so it’s just normal snakiness.

This puns on a now archaic meaning for error as simply wandering, such as a knight errant (i.e., a wandering knight). Like many poets and writers of the early modern era (think Shakespeare), Milton was great with puns.

Raphael’s simile hearkens back to the action-packed war in Heaven, between the armies of Satan and God, that he’s just narrated.

Sure, the waves are just figurative armies, but the creation of the waters is still really exciting and would probably make a great movie.

Least=lest

Raphael tried to show Adam the follies of the angelic “Apostates” (i.e., Satan and his rebellious crew) so that something similar won’t “befall” him and Eve

In both cases, what “befalls” those who disobey God is precisely a “fall,” either from Heaven or from grace.

Milton was a champion punster.

Bellerophon tried to fly to Heaven, but Zeus sent a horsefly to sting Pegasus, and Bellerophon fell off, and got stranded on some random plain

Milton acknowledges he’s being even more hubristic than that (remember, Heaven is way higher than anything the Greeks could even imagine)

But he still hopes he won’t “fall / Erroneous” (“error” coming from the Latin errere, “to wander” – Milton at times suggests that “erring,” at least in Eden, could just be innocent wandering).

Milton is super appreciative of Heaven’s hospitality. It was especially nice of Urania to “temper” the air up there so that the merely human Milton wouldn’t pass out from the lack of oxygen. The thanks, like his hedging on the muse’s name(s), show that for all his courage and moxy, Milton has some humility. After all, he straight up admits the task is presumptuous.

This echoes the idea, in the previous books, that the difference between (prelapsarian) humans and heavenly beings is of degree, rather than of kind, so that Adam and Eve can maybe, one day, “by gradual scale sublim[e]” themselves into angels

Milton invokes a Christian muse, who lives in Heaven, which is way above the pagan gods just chillin on Mt. Olympus

“Urania” just means “heavens” in Greek, so he’s basically asking her to descend from herself, but whatever, “the Name” is less important than “the meaning,” which is that Milton is getting inspired by the divine power of God.

Like the invocation of the muse in Book 3, Milton again expresses uncertainty concerning the proper name and address of his muse: “by that name / If rightly thou art call’d.” This says something about Milton’s humility. Sure, it takes serious ego and courage to “justifie the ways of God to men,” but hedges like this reveal that Milton is a little hesitant when it comes to naming his heavenly muse. For all his chutzpah, he understands he needs to tread carefully.

The idea that Africa is a “dark continent,” inscrutable to Western understanding, persists today

The fact that Ethiopia, like “Nature,” is female here calls to mind Freud’s declaration that female sexuality is a “dark continent”

Freud says: “le G-spot n'existe pas”

Christ’s Second Coming is narrated in the biblical
Book of Revelation.

In the post-WWI era (Yeats wrote this in 1919), in the aftermath of what was a staggering loss of life at the hands of man, western society found its belief structures, including religion, falling apart.

In this analogy, the falcon represents society, and the falconer (who should be commanding the falcon) represents God or some equivalent source of intellectual and moral certainty. The falcon’s gyre is supposed to shrink as it comes nearer to the falconer, but instead the gyre is widening, suggesting that man or society is getting farther and farther from our objective or from God.

The loss of transcendental certitude was a common theme in post-WWI era literature. (See, for example, T. S. Eliot’s The Waste Land.)

Notice that the “falcon"—not the human falconer—occupies the place of subject here, contrary to what we might think of as the natural hierarchy. This reversal reinforces the revolutionary and tumultuous change within the narrative. The dissonance ("cannot hear”) implies the incompleteness—through fissure and discord—of the poem, as well as a failure of understanding that may serve as an implicit warning to the reader. A broken teleology (in that the “falcon” cannot fulfil his purpose/teleology) and a climate of antithesis pervade the line, and the poem as a whole.