There has been a longstanding debate in epistemology over the role of reason in cognition. The empiricists argue, roughly, that all knowledge is derived from observation (sensory experience and introspection), and that the role of reason is therefore only to operate on, or make inferences from, the information provided by experience. In contrast, the rationalists say that we have some substantive knowledge that is independent of experience, and that the faculty of reason can be a source of new knowledge.