The logico-epistemological nature of ontic and ontological arguments

In the paper I explore van Inwagen’s distinction between ontic and ontological arguments, the latter being a special case of the former. An ontic argument proves the existence of some entity; an ontological one proves the existence of a deity. Both are based on a single premise which specifies a set of properties exemplified by an entity of the sort in question. This set van Inwagen calls an ontic set, and he defines the ontic set of an ontological argument in a way which secures the semantic validity of the argument. I argue that an ontological argument is neither immediate nor semantically valid, but that, contrary to van Inwagen’s contention, it is rational to accept its conclusion. In my argument for this claim I rely on C.I. Lewis’ notions of intension and comprehension. Although I disagree with van Inwagen’s formulation of ontic arguments, I do not reject it as a whole - its considerable advantage is, I suggest, in blocking an objection (which allegedly follows from Fregean semantics) that the sentence “God exists” is not well formed. Consequently, part of the paper is devoted to the analysis of existential propositions. The argument I give in favour of the rationality of believing in the conclusion of an ontological argument is based on identifying and avoiding the step which leads to a generalization resembling the one that generates Kyburg’s lottery paradox