Paul Gagnon, author of the article mentioned by CA Ely in response to this post, was the lead staffer for the Bradley Commission on History in the Schools, which was run out of UCLA (depts. of hist. and ed., as I recall). The Commission's summary report is a superb and pithy answer to the question. And it does not recycle the old saw about " . . . condemnded to repeat . . ." Highly recommended. Matt Roth