Common Sense Rationalism

My aim in this essay is to defend rationalism, the view that some propositions expressed by synthetic sentences can be justifiably believed on a priori grounds. More specifically, I defend the following principle of epistemic justification: IPC (intellectual phenomenal conservatism): If it intellectually seems to S that p, then, in the absence of defeaters, S thereby has at least some degree of a priori justification for believing that p. IPC says that intellectual seemings (or appearances)—mental states with propositional content that are neither beliefs nor experiences—are a source of a priori justification. Since it permits beliefs whose contents can be expressed by synthetic sentences to be justified a priori, IPC is undoubtedly a rationalist principle. IPC is an instance of Michael Huemer’s general principle of Phenomenal Conservatism, which says, roughly, that, absent defeaters, all seeming states provide some degree epistemic justification. Phenomenal Conservatism, is, in turn, inspired by the Common Sense approach to epistemological methodology associated with Reid, Moore, and Chisholm. Thus, my defense of rationalism proceeds, by five steps, from (broadly) Common Sense presuppositions. First, I provide a theoretical definition of rationalism and an analysis of its constituent concepts. Second, in light of this definition, I identify four bodies of evidence that provide prima facie support for rationalism. Third, I argue that empiricist explanations of this evidence are inadequate. Fourth, I exposit and defend the principle of phenomenal conservatism and, by extension, IPC. Finally, I argue that a successor principle, RPC (a) adequately explains our prima facie evidence for rationalism, (b) is more attractive than competing versions of rationalism, and (c) withstands the main objections to rationalism.