Two questions are central to the “rationality debate” in the philosophy of social science. First, should we acknowledge differences in basic norms of epistemic and agential rationality, or in the content of perceptual experience, as the “best explanation” of radical differences in belief and practice? Second, can genuine understanding be achieved between cultures and research traditions that so differ in their beliefs and practices? I survey a number of responses to these questions, and suggest that one of these, “dialogical optimism”, (...) while attractive, is in need of further clarification. Such clarification may be forthcoming if we attend to recent work by John McDowell. McDowell claims that perceptual experience, as our primary mode of epistemic access to the world, must be located within what Sellars termed the “space of reasons” if we are to make sense of our conception of ourselves as thinking creatures. I develop a reading of this claim in terms of a fundamental duality in human perceptual experience, and use this conception of experience to illuminate the dialogical optimist strategy in the rationality debate. (shrink)