Environmental politics often asks for our renunciation – for example by reducing waste or driving less. These contemporary forms of asceticism may seem remote from traditional Christian forms, and yet, even religious renunciation has often had political significance. This talk asks about the political significance of asceticism, especially in the work of Henry David Thoreau and Thomas Merton. It argues that Thoreau’s nineteenth-century retreat described in Walden was playing on more ancient monastic practices, and that Thomas Merton was an inheritor of this vision of ecological justice. Thoreau and Merton demonstrate the political significance of asceticism in an ecological age, and they offer lessons for contemporary struggles for justice.