Attempts to explain human behavior date back to the dawn of time. Questions relating to motives, motivation, and volition have been addressed from various perspectives under different labels and have prompted a variety of explanatory models. What is common to all these attempts is that they seek to establish the reasons for actions; their individual differences; and for the activation, control, and persistence of goal-oriented behavior. It would go beyond the scope of this chapter to review the intricate and involved history of this endeavor (see Bolles, 1975, for such a review). What Hermann Ebbinghaus (1850–1909) supposedly said about psychology, namely, that it has a long past but a short history, applies equally to the study of motivation.