(I) Man differs from the lower animals because he preserves his past experiences. (II) In recent decades a growing number of historians have embarked on research in political and social history. (III) What happened in the past is lived again in memory. (IV) With the animals, an experience perishes as it happens, and each new doing or suffering stands alone. (V) But man lives in a world where each occurrence is charged with echoes and reminiscences of what has gone before, where each event is a reminder of other things.