Find out the cause of this effect,
Or rather say, the cause of this defect,
For this effect defective comes by cause.

– William Shakespeare

Hamlet, Act 2, Scene 2. Polonius tells Claudius and Gertrude that they must find out the cause of Hamlet’s madness. Hamlet, he claims, fell into his madness when he told his daughter Ophelia not to see Hamlet anymore, and she followed his advice.