On April 20, 1951, Leon Van Hove presented his thesis "Sur certaines representations unitaires d'un groupe infini de transformations" to the Universite libre de Bruxelles (Free University of Brussels), two days before the University of Grenoble had approved the creation of L'Ecole d'ete de physique theorique at Les Houches (Haute Savoie, France). The first session of the "Ecole des Houches" began on July 15, 1951, with a month-long course by Van Hove on quantum mechanics. The lecture notes for this course were written for the benefit of physicists who -like most of their colleagues outside...