“He who knows only his own side of the case, knows little of that”
– John Stuart Mill
From On Liberty (1859). Mill’s point: holding a true opinion isn’t the same as understanding it. If you can’t argue the other side in its strongest form — not the caricature your side passes around — you don’t actually know why yours wins. You’ve just inherited a conclusion. Belief untested by real opposition, Mill says, hardens into dead dogma: a formula recited, not a conviction held.