The paper offers a contribution to the descriptive, experiental psychology of drives. Major bodily needs are mirrored in consciousness in the form of motivational experiences. The author distinguishes spontaneous from reactive motives and differentiates three groups of motives occurring in inner life: pure pleasure motives, pain-pleasure motives, and pure pain motives. Pain and pleasure, the regulatory principles of psychic events, are involved fourfold in the process of deliberate decision-making; and it has been overlooked in conventional accounts which have dealt only with drive influences and intellectual control factors. An analysis of the dynamics of will shows that the 'posture of the ego' with respect to conflicting modes consists essentially in determining, by means of a trial decision, which impulse is most in accord with the general purpose of the ego (the need to secure happiness) and to identify with this impulse.