在数学中 ,要证明一个命题成立。需严格论证在所给的条件下能逻辑地推导出结论。而要证明一个命题错误 ,十分简洁而又极具说服力的办法是举出反例。反例的威力来源于形式逻辑 ,举出反例则能否定命题是以排中律为保障的。美国数学家Ｂ .Ｒ .盖尔鲍姆说 :“冒着过于简单化的风险 In mathematics, it is necessary to prove that a proposition is true. It is necessary to rigorously demonstrate that the conclusions can be logically derived under the given conditions. To prove a propositional error, a very concise but convincing approach is to give a counterexample. The power of counterexamples derives from formal logic, and counterexamples can negate the proposition that it is guaranteed by Paizhong’s law. The American mathematician B.R. Gailbaum said: "The risk of oversimplification