This essay historicizes the concept of nature in French anarchist pedagogy around 1900. I argue that anarchist cosmology was not dualist in the sense that it did not neatly separate the natural from the cultural or social. Nature was rather understood as an ever-evolving realm that encompassed nonhuman and human entities. This example should encourage historical scholarship to look more deeply into what anthropologists sometimes call “naturalist ontology”. Instead of conceiving it as a fixed worldview, we should investigate its genealogy, transformations, and contestations.