 The issue here is an instance of something more general. Supervenience plays a useful role in answering questions about the identity and individuation conditions for things belonging to some kind. As Davidson pointed out, there is a prima facie puzzle (1980, ch. 5) about how to address such questions. The answer to the question “When are two events identical?” is trivial—“Never.” And the answer to the question “When is an event identical with itself?” is likewise trivial—“Always.” But surely there is a substantive question lurking here. Davidson himself opted to get around this worry by means of semantic ascent. But an alternative is to move to what David Lewis calls ‘a nonduplication principle’ (see Bennett 1988). Instead of asking when two events are identical, we can ask a fill in the blank question: ‘no two events can be just alike with respect to ______’? Davidson would fill in the blank with ‘their causes and effects’. Kim would fill in the blank with ‘their subject, time, and constitutive property’ (1976); others fill in the blank in other ways.