"Infant Joy" is an uplifting dialogue between a newborn speaker and an adult figure—perhaps the baby's parent, perhaps the poet-narrator voice that appears throughout Songs of Innocence and of Experience. The "infant" of the title, unexpectedly enough, gets the first words, telling the grown-up its life story to date: it has "no name" yet, and it's only "two days old."
This baby speaks in simple, monosyllabic words, and often in dimeter (that is, lines of two stresses apiece) or trimeter (lines of three stresses), like so:
I have no name
I am but two days old.—
These short, simple lines feel fitting for a speaker who's only lived for two days so far!
Both of the baby's first two lines start with the word "I." This anaphora reminds readers that this new little self is just getting to grips with having a separate life and identity: with "no name" and only "two days" on earth, it still seems to be enjoying the novelty of being an "I" at all.
The poem, too, honors this baby's independence. Blake's poetry deeply values childhood, often depicting it as a pure, free, instinctive, and ecstatic state. It's telling, then, that the first words in this poem belong to the infant, rather than the adult—and that the adult replies to the baby's declaration that it has "no name" with a respectful question: "What shall I call thee?"
Newborn babies, of course, are usually named by their parents, so there's a role reversal here. The adult speaker gives this decision back to the child, giving the infant's perspective priority. Children, these first lines suggest, deserve respect as independent people from the moment they're born.