Byron's "Don Juan," Canto I, st. 93

In thoughts like these true wisdom may discern
  Longings sublime and aspirations high,
Which some are born with, but the most part learn
  To plague themselves withal, they know not why;
'Twas strange that one so young should thus concern
  His brain about the action of the sky:
If you think 'twas philosophy that this did,
I can't help thinking puberty assisted.

At this point in Byron's hilarious Don Juan, the young eponymous hero has just begun to emerge from his quirky moral education. Juan and the beautiful Donna Julia are falling in love, but Juan recognizes that, because Julia is married, any potential relationship is illicit. Recognizing his danger, Juan tries to distract himself. He wanders in the "leafy nooks" and seeks "self-communion with his own high soul"—Byron's parody of the stereotypical stance of the Romantic Poet (he mentions Wordsworth and Coleridge by name). And Juan tries to distract himself with sublime thoughts about astronomy, philosophy, and "the many bars / To perfect knowledge of the boundless skies." These are examples of the "Longings sublime and aspirations high" in the second line of the stanza quoted above.

Ordinarily we think of such "aspirations high" as motivated by some purely intellectual or spiritual calling. One seeks "perfect knowledge" as an end in itself—that which is beautiful or good or true (to borrow the Platonic trinity) is its own self-justifying end, and such perfection is typically assumed to be an intellectual or spiritual pursuit far removed from and unsullied by the base appetites of an actual physical, sexually interested body. The comedy of Byron's poem depends in part on his linking of the base and physical with the intellectual and spiritual. In the process, the "lofty" or "sublime" becomes a kind of side-effect of thwarted sexual desire—"If you think 'twas philosophy that this did, / I can't help thinking puberty assisted." The supposedly transcendent is brought crashing down to earth with all the slapstick of a dreamy stargazer slipping on a banana peel.

One way to understand what makes Byron's later poetry so funny is to consider a rhetorical figure called a "zeugma." With its origins in the Greek word meaning "yoke" (as one might yoke oxen together to pull a heavy load), "zeugma" has come to mean a yoking together of dissimilar elements. A corny example:

The senator departed for the statehouse, his mind inflamed by lofty principles and cheap bourbon.

Here the "lofty principles" that one might expect from a senator are yoked together with "cheap bourbon"—both are, in fact, parallel objects of the preposition "by," both are elements that might affect (albeit in very dissimilar ways) the senator's mind. The "lofty principles" are thus brought into a distinctly worldly context and the result, if all goes well, is the reader's knowing laughter. Pretensions are exposed, hypocrisy skewered. Byron's poem often adopts a form of zeugmatic thinking in order to produce its own sort of comedy. In the passage above, for example, poor Juan is himself motivated by both "philosophy" and "puberty"—one lofty and transcendent impulse, the other very physical and worldly. (An instructive exercise, by the way, is to identify passages that seem most likely to inspire the reader's laughter, and then see whether there is some zeugmatic structure involved.)

The point is particularly significant in light of romanticism's preoccupation with the connections between the human/natural world and some supernatural realm beyond (as captured in the title of a classic of romantics criticism from the mid-2000s, M. H. Abrams's Natural Supernaturalism). Byron, in an earlier moment in his career, descibed the condition of humankind as suspended between "dust" and "deity" and thus belonging to neither realm and perpetually discontent. In Manfred, unless one reads the drama as parody, this condition led to a kind of anguished and self-destructive alienation. Here in Don Juan, the "dust" and the "deity" are also linked, but the result now is laughter.