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I am not young enough to know everything.
— J.M. Barrie ‧ The Admirable Crichton

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
This is a witty take on confidence and age. The speaker says they're too old to claim knowing everything, since experience has taught them how much they don't know. Certainty, in this joke, belongs to youth.
Context reviewed