Every generation must learn these lessons afresh, must find by its own experience that evil traits will invite the purgation of suffering. Technical advance can be kept for and maintained by the next generation, but spiritual advance is a highly personal and individual matter. It drops out again when the man himself drops out of circulation. This is why real historians who happen also to be deep thinkers tell us that mankind's moral nature changes only slightly during the centuries. The group has to learn its moral lessons all over again but some units in that group need not.
-- Notebooks Category 13: Human Experience > Chapter 1: Situation > # 58