Abstract: This essay discusses the relation between philosophical reason and sociological rationality from the three perspectives of etymology, concept development, and concept feature. From etymology, reason is inclined to be a concept of philosophical ontology and epistemology while rationality, in a large degree, belong to a sociological concept that concerns people’s thinking, learning and assessing. And from concept development, both experience five phases: ancient Greece, the ontological reason of medieval times, the epistemological reason of early modern times, the sociological rationality of enlightenment, modern rationality and postmodern rationality. All these five phases display a gradual process from philosophical reason to sociological rationality. And from their respective features, reason emphasizes transcendentalism and absolute generality while rationality emphasizes empiricism and relative generality.

Key words: rationality, philosophy, sociology, reason