Columbia College Today has a fine article about cultural historian Jacques Barzun. Here's my favorite passage, from an interview with Barzun in American Educator:
The student who reads history will unconsciously develop what is the highest value of history: judgment in world affairs. This is a permanent good, not because history repeats -- we can never exactly match past and present situations -- but because the "tendency of things" shows an amazing uniformity within any given civilization. The great historian Jacob Burckhardt said of historical knowledge, it is not "to make us more clever the next time, but wiser for all time."
Plus, a person endowed with the knowledge of history reacts a good deal more serenely and temperately to the things that he encounters both in his own life and in the life of the country in which he lives. Besides which, history is a story -- full of color and dramatic events and persons, of triumphs and dreadful actions, which must be known in order to form a true notion of humankind.
His conclusion about the meaning of history is this:
I have always been -- I think any student of history almost inevitably is -- a cheerful pessimist.
Given the tremedous progress in human well-being over the last thousand years, I'd prefer the term "tempered optimist".