I begin by examining the answer to a traditional puzzle concerning supererogatory acts: if they are good to do, why are they not required? The answer often given is that they are optional acts because they cost the agent too much. This view has parallels with the traditional view of religious sacrifice, which involves offering up something or someone valuable as a gift or victim and experiencing a ‘cost’ as part of the ritual. There are problems with the idea that (...) costs justify the optional nature of supererogatory acts, however, and I suggest that these problems mirror the tensions that are found in Christian theology when a traditional view of sacrifice is adopted. (shrink)