As described in George Herbert Mead's 'Mind, Self, and Society':

"History is largely occupied in tracing out the development which could not have been present in the actual experience of the members of the community at the time the historian is writing about. Such an account explains the importance of history. One can look back over that which took place, and bring out changes, forces, and interests which nobody at the time was conscious of. We have to wait for the historian to give the picture because the actual process was one which transcended the experience of the separte individuals." (256).


One might add that the historian enjoys a provisional topsight on the actions of the past. The 'actual process' has become visible with hindsight, and the process as understood by contemporaries appears as a limited perspective, or blind to the truly relevant forces at play, or to their resulting combination. The historian is inherently a time traveller, and a paradoxical one: he cannot do without the perspective contemporary to the events, and he cannot do without the later perspective which puts the former in perspective.