method to one's madness

Example: “He labels every sock, but there's a method to his madness.”

Origin: Adapted from Shakespeare's Hamlet (c. 1600–1601): watching Hamlet's erratic behavior, the courtier Polonius remarks to himself, "though this be madness, yet there is method in't" — recognizing, correctly, that Hamlet's apparent insanity is actually a calculated performance concealing a deliberate plan for revenge. The modern idiom rearranges Shakespeare's original word order into the more natural "method to one's madness," but keeps his exact insight intact: behavior or a plan that looks chaotic or irrational on the surface may in fact be following a coherent, purposeful logic that simply isn't obvious to an outside observer.