LANDE:Concerning “the historical origin of the dualistic interpretation” which I “have not realized:” I know of course of Einstein's light quanta in opposition to light waves. But I also know that there is a unitary quantum theory of radiation that has relegated the “photon” to the role of a quantum number attached to the periodic components of the continuous Maxwell field; thereby it has become unnecessary to attribute variousad hocinvented quantities—spin, interdependence of electric and magnetic properties of the photon—in order to save a particle picture dual to the wave picture of light. Light waves are real, matter waves are imaginary, in more than one sense.