“He who knows only his own side of the case knows little of that.”John Stuart Mill · Despre libertate · 1859 · Capitolul 2
You don't know your own position until you can state the opposite one fairly and fully.
Mill argues that genuinely understanding a position requires knowing the objections to it. Only then do you know why your position holds, where it is weak, and what answers are needed. Someone who reads only sources confirming their beliefs repeats slogans rather than grasping causes. A well-prepared lawyer studies the opposing file as carefully as their own: that is precisely what makes them able to defend the case.
Why it matters A practical test for any debate: if you cannot state the opposing view fairly, you are not ready to challenge it.