Empiricism is an ism with many meanings. In accounts of the history of philosophy, empiricism is often contrasted with rationalism, though serious historians frequently look with jaundiced eye at this way of telling the story. According to this formula, empiricists emphasize the role of sense experience, rationalists the role of reason. Each position can be given extreme formulations, as in the clashing claims that sense experience is the only source of knowledge or that reason is, and each position can be moderated, with the attendant possibility that they no longer conflict. The debate was usually framed in terms of the existence of “innate ideas” and often blurred the distinction between psychological and epistemological questions.