When I was a boy of fourteen, my father was so ignorant I could hardly stand to have the old man around. But when I got to be twenty-one, I was astonished at how much he had learned in seven years.

The quip turns a familiar adolescent experience into a pointed joke about perspective. At fourteen, the speaker mistakes his own immaturity for superior insight and reads his father’s limits as “ignorance.” By twenty-one, the speaker’s widened experience makes him reassess the same father and recognize that the change was largely in himself. The punchline—crediting the father with having “learned” so much—highlights how youthful certainty can be a form of blindness, and how growing up often means discovering the depth of older people’s judgment. It’s also a compact satire of self-importance: the son’s earlier contempt is exposed as the real ignorance.