In defining the principles of occlusal function it is possible to demonstrate how firmly the number, the placement and the distribution of occlusal contacts control muscle activity and joint function during biting and chewing. This control implies that the intercuspal position is determined by positive feedback, that is by afferent activity that varies with occlusal stability. Conventional dental treatment involving occlusal surfaces alters this input and consequently alters the coordination of the muscles of mastication and the function of the temporomandibular joints. To assess and direct this input properly, quantitative parameters of electromyography and kinesiography are needed. Terms such as harmony and disharmony are irrelevant and must be abandoned.