This essay argues that the neo-Roman republican principle of "non-domination," as developed in the recent work of Philip Pettit, cannot serve as a single overarching political ideal, because it responds to only one of two important dimensions of concern about human agency. Through critical engagements with several aspects of Pettit's work, ranging from his philosophical account of freedom as "discursive control" to his appropriation of the distinction between dominium and imperium, the essay argues that the idea of domination, which responds (...) to concerns about "control," needs to be supplemented by the idea of usurpation, which responds to questions about "involvement"; and it shows how attention to both domination and usurpation (and to the interaction between them) can shed light on such phenomena as imperialism, slavery, and democracy. (shrink)