This article discusses a general class of theories that attempt to base a normative accountof justice on consent-giving procedures. Contemporary political philosophersoffer many different accounts of justice, but at present consent-based theories areprobably the most popular. Notwithstanding their (often understandable) appeal, Iwill argue they cannot possibly succeed. All consent-based theories trade on a crucialambiguity as to whether they are supposed to be understood as voluntarist accountsof justice on the one hand, or as rationalist accounts on the other. In the formercase, consent-based theories fail because they are at best indeterminate and at worstincoherent; in the latter case, they fail because they are superfluous. I will refer tothis fatal ambiguity as “Cassirer’s Dilemma.” Interestingly, Cassirer’s Dilemma is notat all new, on the contrary, it may be among the olde...