Themes
The old believe everything, the middle-aged suspect everything, the young know everything.
— Oscar Wilde

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The line sorts three stages of life by attitude. Age accepts every claim, midlife doubts them all, and youth is certain it already has the answers. Wilde's neat symmetry mocks each group gently: credulity, cynicism and overconfidence each get a turn, with no stage escaping.
Context reviewed