"The continuing evolution of our idea of time is revealed by the increasing importance of tense in the development of language. Greater knowledge of the universe has been accompanied by greater appreciation of the distinction between past, present, and future as people have learned to transcend the limitations of 'the eternal present'. Although our awareness of time is based on psychological factors and on physiological processes below the level of consciousness, ...it is also dependent on social and cultural influences. Because of these, there is a reciprocal relation between time and history. For, just as our idea of history is based on that of time, so time as we conceive it is a consequence of our history."