When Charles Lyell chronicles humankind's rise to geologic power in the Principles of Geology, he talks out of both sides of his mouth. Detailing the human species’ seemingly unmatched force as a terrestrial “levelling agent,” he ruminates on an unsettling possibility that haunts the present: “it admits of reasonable doubt whether, upon the whole, we fertilize or impoverish the lands we occupy.” Already at the time of Lyell's writing, the human species had “displaced” or altogether extinguished “a number of beasts of prey, birds, and animals of every class” (2:148) through deforestation, hunting, and the “progress of colonization” (2:150–51). But elsewhere in the Principles, Lyell puts into question what this history of environmental degradation otherwise seems to assert: that to be human is to possess a singular capacity for mastery. Thus, Lyell declares, “we ought always, before we decide that any part of the influence of man is novel and anomalous, carefully to consider all the powers of other animate agents which may be limited or superseded by him” (2:206). Tracing how swarms of insects gave dramatic and lasting shape to the German arboreal landscape in ways that humans could never replicate, he concludes: “[I]t does not follow that this kind of innovation”—human innovation—“is unprecedented” (2:206). Even as Lyell imagines humankind as “superior” in its capacity to act as “a single species,” he persistently lingers with the very real possibility that humans do not possess a “novel and anomalous” hold over the world (2:207, emphasis original). Instead, the Principles traces how the world is shaped by “physical causes” and nonhuman agencies that elude control and unmask the relative “insignifican[ce]” of humankind's “aggregate force” (2:207). Inasmuch as humans comprise only one part of an agential assemblage whose shifting interactions elude anthropogenic mastery, the Principles imagines humankind as interpenetrated by and profoundly susceptible to nonhuman life-forms and forces. According to Lyell, then, deep history speaks not only of the human species’ seemingly privileged capacity for action but also its nonintentionality, noninstrumentality, and vulnerability. That the Principles tells a story about the porous interfaces between human and nonhuman geologic agents is perhaps surprising, given that it emerged and participated in a moment which, for many, marks the zenith of imperial and anthropogenic power.