Swinburne gives himself four chances to describe a baby, and each time the poem admits it hasn't quite managed. That admission drives "Babyhood." Every numbered section returns to a refrain ("A baby," "All heaven," "What likeness may," "Rose"), and every section says in some form that words fall short. Love "cannot praise aright," "can say not," and knows of "no song" that will do. The praise works by showing how far praise falls short.
The form suits this. Each section runs to eleven lines, grouped 4–3–4, with the opening words coming back as a refrain. This is the pattern of a roundel, a form built on return, and it fits a subject you simply keep looking at. The rhyme is tight and chiming. In the first section only two sounds hold everything together: *bright, sight, light, night, aright* on one side, and on the other *May be, grey be, midday be*. The refrain "A baby" slips into that second group, since "baby" and "may be" sound alike. The word seems to dissolve into the small, unfixed phrases around it, as if the baby were what "may be" in every season and every hour. In the second section the rhymes are *heaven, leaven, forgiven, given, seven*, a run of soft, open sounds that the refrain rejoins.
The refrain also finishes the sentence each time. "On eyes that keep in sight / A baby" lands the reader's gaze on its object, like a look settling. The third section plays a trick with this. At first "Love can say not / What likeness may" reads as a plain statement. The last refrain, "What likeness may?", comes back as a question with no answer.
The imagery narrows as the poem goes on. Section one is all light: the baby "shines," fills "our eyes with light," and ignores winter and May, midnight and midday. Section two goes up to theology. "Heaven" is revealed "in every baby born," free of "earthly leaven" (the yeast that works through dough, which suggests contamination). The word "all" piles up: "all sin forgiven, / All grief appeased, all pain outworn." The claim is large, and the poem knows some will "scorn" it, but it doesn't back down.
Section three tests ordinary comparisons and lets them fail. The Mayflower, satin, swansdown and buds are each offered and found wanting. The rhyme words themselves are refusals: *say not, stray not, stay not, play not, may not*. Even the buds lose, because they "play not / As yet with winds that play." They are too still beside a living child.
Section four is the smallest. The lines shrink to a few syllables, and the cosmic scale of "heaven" gives way to one flower. The sleeping child's head shows between the bed's curtains, like a rose among "Dawn's cloudlets," and the poem addresses the flower directly: "Rose!" Only at the end does the address become an identity: "The whole child glows / One sweet live red / Rose." Here the refrain stops being a name called out and becomes a metaphor that has come true. The word "live" matters, because the rose breathes in a way satin and swansdown cannot.
The poem's significance lies in this movement, which is also an argument. Big words (heaven, sin, forgiveness) and careful similes both give out, and a small, exact image does what they could not. The vocabulary is mostly short and plain, and nearly all the effect comes from sound, repetition and placement. Swinburne is known for musical verse, and here that skill serves a modest subject. He gives an ordinary baby the language of revelation, then lets the revelation settle into a flushed face behind a curtain, just before waking.