Is There a Difference Between Aristotle and Abilard?

All My Life is a half-million word book about the history of philosophy. The author says he was surprised by what he found in his research for the book. He has written books on Aristotle, Aquinas, Descartes and Wittgenstein among others. In the final volume I think Husser was really the person that I realized I'd completely underestimated - Schopenhauer which took me quite by surprise.