Carl Jung brought an almost mystical approach to psychodynamic theory. An early associate and follower of Freud, Jung eventually disagreed with Freud on too many aspects of personality theory to remain within a strictly Freudian perspective. Subsequently, Jung developed his own theory, which applied concepts from natural laws (primarily in physics) to psychological functioning. Jung also introduced the concept of personality types, and began to address personality development throughout the lifespan. In his most unique contribution, at least from a Western perspective, Jung proposed that the human psyche contains within itself psychological constructs developed throughout the evolution of the human species.