How is revolutionary philosophy sounded by poetry? This paper explores perception and materialism in Percy Bysshe Shelley’s teenage writings, frequently dismissed by critics as juvenile and lacking in philosophical complexity. By approaching the role of dreams, the imagination, and perception in Shelley’s poem Queen Mab alongside contemporary translations of Lucretius’s poem De Rerum Natura I show that the poem’s philosophy of matter is more subtle and sophisticated than has been previously thought, as ‘contingency and chance’ operate via necessity that is built into the laws of nature. I discuss how Shelley used the material technology of the printed book and the poem’s sounded dimension to challenge readers’ perception of matter, connecting the freedoms of poetic thought to the coming-into-being of a future political utopia. I conclude by considering why it is important to reconsider the status and politics of matter in Romantic poetics, and how such a poetics contributes to our historical understanding of more sensitive and attentive forms of life.