Idiom
exception that proves the rule
Theme: PROOF
a saying claiming that when an exception has to be made to a particular rule or guideline, this simply emphasizes the existence of the rule. (The exception tests for the existence of a rule. Usually with the.)Sixth-graders do not have to wear school uniforms, but they're the exception that proves the rule.The youngest dog is allowed in the house. He's the exception that proves the rule.