This essay examines two interrelated strategies Shelley uses to conceive of the systemic context for individual agency. In both cases, Shelley portrays agency as moving or acting upon air. First, drawing on new scientific accounts, Shelley examines the weather as a global system that is subject to local variability. Comparing the movement of weather to the movement of ideas, Shelley postulates that systemic change occurs when air from a “free” region moves into and temporarily disrupts air that has been tainted by despotic social and political structures. In this analogy, weather provides a model for the action of poetry because air is the medium through which the poet acts on readers by literally changing their breath. And the second way Shelley explores the possibility of systemic change is through adopting and altering poetic form to move readers’ breath. Poetic form proves such an important resource for Shelley not only because it shapes readers’ breathing to its metrical patterns but also because, originating in another era, it stands apart from current sociopolitical systems. In Laon and Cythna, Shelley envisions the caesura within the Spenserian stanza as a tool for moving systemic structures.