 What matters here is just that nonduplication principles are supervenience theses. They are supervenience theses that take the supervening set A to be the identity facts for particular entities of whatever kind is in question. There cannot be a difference in whether an event has a property like being event e without a difference in its causes and effects (Davidson) or in its subject, constitutive property, and time (Kim). Note that any view that accepts a nonduplication principle for some sort of entity is ipso facto anti-haecceitist. Both Davidson and Kim are anti-haecceitists about events.