Before the child says a word, Blake has already unsettled us by calling him "a little black thing in the snow." He is not a boy or even a child but a *thing*, as if the passer-by who stops to question him sees an object that has wandered into the street. The blackness is presumably soot, and it stands out starkly against the white. His cry, "weep! weep!", sounds like a child's mispronunciation of "sweep", the call of the trade named in the title, but it also does what it says. Advertisement and grief collapse into one word.
The form is deceptively light. Four-line stanzas, a bouncing rhythm of about three or four beats a line, and tidy rhymes give the poem the feel of a nursery verse. The first stanza pairs its rhymes (snow and woe, say and pray) and plays out as a quick exchange, a blunt question and a flat answer: "They are both gone up to the church to pray." The questioner's formal "thy" makes the child's plain reply sound even more matter-of-fact. In the two stanzas that follow, the rhymes interlock (heath with death, snow with woe), and the music keeps its sweetness while the meaning turns sour. That clash is the poem's chief effect: a jingle carrying an accusation.
The second stanza is built on the word "because". The boy was "happy upon the heath" and "smiled among the winter's snow", so his parents "clothed me in the clothes of death." The logic is horrifying, since happiness is treated as an offence to be corrected. The snow has changed meaning too. In the first line it was where a lost child cries, and here it is a place where he once smiled. The verbs "clothed" and "taught" make the parents the only actors and leave the child passive. "Clothes of death" suggests a sweep's sooty outfit, and the phrase also hints at a shroud. Then comes the quiet shock of the line "And taught me to sing the notes of woe." The "notes of woe" that the stranger heard in line two return here, and we realise the weeping was a lesson. What sounded like spontaneous misery was a performance learned by rote.
In the final stanza the child sees through the whole arrangement. He still "dance[s] and sing[s]", and his parents take this as proof that they "have done me no injury." The word is chillingly small, closer to a legal or medical term than to the cruelty it covers, and the child's cheerfulness has become their alibi. His own voice is sardonic, not self-pitying. He understands exactly how the excuse works.
The last two lines widen the target. The parents go to "praise God and his priest and king," a list that climbs in rank and ends in the crown. Blake's "his" joins priest and king to God as if they were God's property, or God theirs. Then comes the sharpest phrase in the poem: "Who make up a heaven of our misery." "Make up" can mean to construct, and it can mean to invent, so this heaven is both built from suffering and a fabrication. The shift from "I" to "our" also turns one boy's story into the condition of many. The long, sliding rhyme of "injury" and "misery" lets the poem end on its heaviest word.
The poem's significance lies partly in what it refuses to do. It does not ask us simply to pity the child, and no rescuer arrives to answer the stranger's question. Instead it points at the adults, the institutions, and the comfort they take from their own piety. The child is the most clear-sighted voice present, and the church-goers are the blind ones. The poem keeps its force because the question it raises is still easy to recognise: who benefits when suffering is explained away, and what do we call it when we pray over it?