Spear and Shield in Contradiction
卖矛与盾者：盾无不陷，矛无不陷——无可同立。成语指言论或立场自相冲突。逻辑入门典故。
A vendor claims a shield nothing can pierce and a spear that pierces anything—both cannot stand. Classic logic idiom for self-contradiction.
检查你的主张能否同时成立。
Test whether your claims can be true together.
After the moral, ask one question: if a similar choice showed up today, where does the story snag? Name that tension first—then take your own step. You need not copy the ancients, only borrow their clarity.