Curie’s hazard: from electromagnetism to symmetry violation

Pierre Curie claimed that a symmetry of a cause must be found in the produced effects. This paper shows why this principle works in Curie’s example of the electrostatics of central fields, but fails in many others. The failure of Curie’s claim is then shown to be of special empirical interest, in that this failure underpins the experimental discovery of parity violation and of CP violation in the twentieth century.