In this essay I argue that Humphry Davy uses the figure of Proteus to illustrate his conception of a world in a state of perpetual change. Over the past four years, 11 417 pages of Davy's notebooks have been transcribed by more than 3500 volunteers from around the world. These have revealed the extent of Davy's poetic output and confirmed his world view that matter is constantly being made, unmade, and made again in new forms. For Davy, atoms are drawn dynamically towards and away from each other, forging new entities through the power of heat, cold, and other chemical interventions. Here, I look at specific instances where Davy's poetry and science are in close proximity to each other, on the same notebook page or in the same notebook, paying attention to Davy's interest in the so-called ‘proteus' fish, which was thought to be able to adapt to life on land or sea at will. Davy saw the mythological figure Proteus as a symbol for chemical change and for the changes that all matter goes through. I will also use this trope to discuss the development of Davy’s ideas from notebook to lecture and published page.