Propositions, numbers, and the problem of arbitrary identification

Those inclined to believe in the existence of propositions as traditionally conceived might seek to reduce them to some other type of entity. However, parsimonious propositionalists of this type are confronted with a choice o f competing candidates - for example, sets of possible worlds, and various neo-Russellian and neo-Fregean constructions. It is argued that this choice is an arbitrary one, and that it closely resembles the type of problematic choice that, as Benacerraf pointed out, bedevils the attempt to reduce num bers to sets - should the number 2 be identified with the set {{0}} or with the set {0, {0}}? An "argument from arbitrary identification" is formulate d with the conclusion that propositions (and perhaps numbers) cannot be red uced away. Various responses to this argument are considered, but ultimatel y rejected. The paper concludes that the argument is sound: propositions, a t least, are sui generis entities.