“What a man knows at fifty that he did not know at twenty is, for the most part, incommunicable.”
Address at Princeton University, "The Educated Citizen" (22 March 1954) http://infoshare1.princeton.edu/libraries/firestone/rbsc/mudd/online_ex/stevenson/adlai1954.html
Context: What a man knows at fifty that he did not know at twenty is, for the most part, incommunicable. The laws, the aphorisms, the generalizations, the universal truths, the parables and the old saws — all of the observations about life which can be communicated handily in ready, verbal packages — are as well known to a man at twenty who has been attentive as to a man at fifty. He has been told them all, he has read them all, and he has probably repeated them all before he graduates from college; but he has not lived them all.
What he knows at fifty that he did not know at twenty boils down to something like this: The knowledge he has acquired with age is not the knowledge of formulas, or forms of words, but of people, places, actions — a knowledge not gained by words but by touch, sight, sound, victories, failures, sleeplessness, devotion, love — the human experiences and emotions of this earth and of oneself and other men; and perhaps, too, a little faith, and a little reverence for things you cannot see.