This essay will address a dilemma in the foundations of naturalistic epistemology. As the title indicates, the focus will be on one of the great nineteenth-century founders of this interdisciplinary enterprise, to wit, Charles Peirce. I shall attempt to illustrate the dilemma by noting a certain ambiguity in Peirce's thought; thereafter I shall outline, and discuss the viability of, what I take to be Peirce's resolution of the dilemma.