ABSTRACT
Modern quantum mechanics developed from wave mechanics by abstracting from its most fundamental features. These are the superposition principle and the linearity of the equation of motion. Any theory finds its justification from experiment, but all the aspects of a successful theory do not gain similar weights from such corroborations. The dynamical development of a theory, such as the transition from wave mechanics to the more general scheme of quantum mechanics, can thus be fully understood only if a few important experimental facts are kept in mind, namely, those whose description really requires that particular sets of principles be valid. The chance is good then that these principles will remain as guides in the development of the theory. Although the experiments that corroborate wave-mechanics are very numerous indeed, most of them are quite similar in their essence. The experiment of electron diffraction may be chosen, or, alternatively, the conceptually even simpler experiment of particle diffraction by two holes.
