Canto XII begins with a fourteen-stanza meditation on the misery of middle age (Byron is now thirty-five, he tells the reader in Stanza 2) and the pleasures of money, which Byron ironically sings the praises of. Money rules the world and even rules love. This meditation is followed by a boast about his youthful success as a writer and literary lion, of which he has lately paid the penalty, a comment on the passing nature of fame, and a tongue-in-cheek plea for procreation, which the Malthusians are currently opposed to.
In Stanza 23, he turns to Juan, at least by name, but it is Juan's ward Leila he takes up. The dowagers in Juan's set have decided that her education had better be taken out of Juan's management and put into that of one of themselves. At this point Byron stops to devote a few amusing stanzas to the young "fortune" who has just made her debut and the stir made about her by other females who wish to arrange a match for her with one of their relatives. This is followed by the admission that the lady who got him (Byron) didn't do so well.
Finally Lady Pinchbeck is chosen by Juan as a guardian for Leila. The author agrees that she is a good choice. She knows the world, she is witty, and her reputation is now safe.
Olden she was — but had been very young;
Virtuous she was — and had been, I believe. (St. 43)
Once again Byron returns to Juan and then leaves him to descant upon the perils of high society for a young unmarried man. If he talks six times with the same single lady, her brother wants to know what his intentions are, and soon he is married. Then there are perils from the coquette, and from the wife who merely wants to be friendly. Such friendships end in lawsuits in England; abroad the consequences are less serious.
But Juan is no novice, and furthermore he is somewhat tired of love. And at first he didn't find the English women pretty. Here Byron stops to analyze the English woman. She has some ice in her and hides half her attractions. She glides into the heart and once there holds on. She does not have as many external graces as the Continental woman, nor is she quite so ready with her smile, but when she is taken with a grande passion, it is a very serious thing indeed, and if there is a disaster she is cast out by society and will not be allowed to return.
Canto XII is, on the whole, amusing and no earlier canto is more brilliantly written. Byron is at his poetic best here; the stanzas flow on with the smoothness of a wide river. There is no faltering or stumbling. The rhymes are as smooth as ever and the expression nowhere superior in the whole poem. Whatever subject Byron takes up, and in this canto he takes up quite a number, he has something worth reading to say about it In spite of the diversity of topics, the canto has a unity of theme — not Don Juan, for he is almost left out altogether — but the English woman of high society. In talking of her Byron is politely cynical and avoids sentimentalism scrupulously. He writes as the uninvolved, experienced commentator who understands the ways and wiles of English woman. In Canto XII and the remaining cantos Byron is more at home with his subject.