What electoral system should a democracy choose? I argue for proportional representation (PR). My main empirical premise is Duverger’s law: under PR there are more viable candidates in district-level elections than there are under single-member plurality (SMP) systems. This matters normatively because autonomy is a core part of democracy's value. Democracy enables voters to author their social and political affairs. But how much one enjoys autonomous authorship of anything is constrained by the diversity of one's adequate options. The fewer adequate options one can choose between, the less will one's choice contribute to one’s autonomy. So PR augments voter autonomy by increasing the diversity of adequate options they have at election time. This argument supports a pure PR system with a single nationwide district, nolegal thresholds for legislative representation, in which voters can vote for candidates rather than just for party lists.