If propositions are unstructured and distinct from sets, there are several possibilities for explaining their identity conditions. First, identity conditions might be specified in terms of possible attitudes. One possibility is this: P=Q if, necessarily whoever believes (asserts, denies, etc.) P believes (asserts, denies, etc.) Q, and vice versa. Second, proposition identity might be reduced to property identity in the manner of Myhill (1963) and Zalta (1983). Thus, Zalta (1983, 72) offers the