Part I Formalism and Interpretation.- Introduction: Nonlocal or Unreal?.- Formalism II: Infinite-Dimensional Hilbert Spaces.- Interpretation.- Part II A Single Scalar Particle in an External Potential.- Two-Dimensional Problems.- Three-Dimensional Problems.- Scattering Theory.- Part III Advanced Topics.- Spin.- Electromagnetic Interaction.- Perturbation Theory.- N-Particle Systems.- Path Integral.- Dirac Equation.