This is a further clarification of the psychological theory underlying the Information System for Vocational Decisions (ISVD), a prototypic, computer-based, interactive, information quidance system, which is intended to facilitate the realization of purpose. The basic purpose paradigm herein comceptualized consists of a description, largely in terms of information theory, of a phenomenon labeled "ideal behavior." Such behavior maximizes the probability of future outcomes which would be both adaptive and satisfying. Two further requirements are delineated: (1) the more information involved in a decision to act, the more predictable the result of the action; and (2) such information as guides an individual's behavior must have been evolved and integrated into a system of goal and feedback by that individual. The bulk of the report then discusses some ways in which such evolution and integration might be developed, and how a purpose mechanism might operate, given that necessary information had been learned. (TL)