We often face a bewildering array of different explanations for the same social facts (e.g. biological, psychological, economic, and historical accounts). But we have few guidelines for whether and when we should think of different accounts as competing or compatible. In this paper, I offer some guidelines for understanding when custom or norm accounts do and don’t compete with other types of accounts. I describe two families of non-competing accounts: (1) explanations of different (but similarly described) facts, and (2) accounts (...) which seem to differ but are really different parts or versions of the same underlying explanation. I argue that, while many types of apparent competitors don’t really compete with customs, there are some that do. I also describe some of the central problems, which suggest that custom accounts will compete poorly with their rivals. (shrink)