ABSTRACTLibertarians are attracted to the self‐ownership thesis because it seems to satisfy four important theoretical desiderata. First, the thesis treats all persons equally by assigning them the same initial set of rights. Second, the thesis gives people the strongest set of ownership rights possible. Third, it assigns persons a determinate set of rights. And, finally, it grounds the libertarian rejection of a duty to assist, benefit, or rescue others. This article argues that these four desiderata cannot be simultaneously satisfied. Specifically, it contends that the first three desiderata can be jointly satisfied only if the thesis merely gives people the right to include their owned bodies in various actions (as opposed to a stronger version of the thesis that gives people permissions to do things with their bodies). However, such an interpretation of the thesis will not satisfy the final desideratum. Thus, libertarians face a tetralemma when defining the self‐ownership thesis.