 Approval voting can be axiomatically characterized in terms of adjusted versions of May’s four condition, extended to the setting of approval balloting. Specifically, approval voting is the unique aggregation rule for approval ballots that satisfies universal domain, neutrality, positive responsiveness, and a strengthened version of anonymity called ‘optionwise anonymity’ (Goodin and List 2006). The latter condition formalizes a principle that Brams and Fishburn informally describe as follows: ‘In effect, the principle of “one person, one vote” under plurality voting becomes the principle of “one candidate, one vote” under approval voting. That is, each voter makes judgments about every candidate under approval voting, so the tie-in of a vote is not to the voter but rather to the candidate’ (Brams and Fishburn 1983: 12). For other axiomatic characterizations, see Fishburn (1978, 1988) and Sertel (1988). For extensions of approval voting to settings in which voters express not only approvals but also full rankings of the alternatives, see Brams and Sanver (2009).