Archaeological theorists employ rival epistemologies (theories of knowledge) borrowed from philosophy to justify and help implement alternative programs for interpreting archaeological data. Epistemological idealism has been used to validate cognitive studies of the past, positivism to privilege behaviorist and processual approaches, and realism to promote a combination of both while at the same time noting the constraints exerted by external reality. It is argued that, viewed from the perspective of biological evolution, these three approaches are complementary rather than competing. All human adaptation to the social and natural environments is cognitively and culturally mediated, while, contrary to the claims of extreme idealists, discrepancies between expectations and observed happenings facilitate more effective adaptive behavior. Any rounded interpretation of archaeological data must take account of mental concepts, sensory perceptions, and conditions external to the individual. Positivist methods and humanistic forms of analysis that focus on subjectivity, agency, and the historical transmission of knowledge are complementary to one another. To understand better what has happened in the past, archaeologists must produce scenarios that are radically different from what has previously been conceived. But these speculations in turn must be subjected to rigorous appraisal if genuine progress is to be achieved. Because of its greater inclusiveness and specific postulates, a realist epistemology, combined with a materialist view of reality, offers the most satisfactory general framework for integrating the best features of all three epistemologies and interpreting archaeological data.