The speaker draws a comparison between himself and a fly that he has thoughtlessly brushed away. He asks if he is like the fly, or the fly is more like himself. He imagines another, greater hand, perhaps that of God, brushing him away some day and ending his private designs. He concludes with the belief that he is indeed like the fly, not in his insignificance to Fate or chance, but in the fly’s significance in the natural world. Just as the fly dances and sings, so does the speaker. Thought is what gives him life and breath, and “the want/Of thought is death.” He takes joy simply in existing, with little thought or worry over what tomorrow may hold.
This five-stanza poem takes on a playful rhyme scheme and meter, despite its serious and somewhat morbid subject. The first four stanzas are ABCB quatrains, each made up of terse lines to communicate the brevity of life, which is the subject of this poem. The final stanza, however, is an AABB rhyme scheme, a pair of rhyming couplets, which lends an even more playful quality to the poem as a whole while offering a moral or coda to the entire work.
This poem also returns to Blake's theme in Songs of Experience of the place of thought in the quality and quantity of human life. The speaker harms the fly with his "thoughtless hand," indicating that thoughtlessness leads to death. Whatever power exists higher than the speaker may also be thoughtless or completely indifferent to human life, but that cannot be changed. The speaker thus resolves to live each moment fully, but his moment of contemplation leads him to this life-affirming conclusion.