The conceptual fragmentation of American psychology is a function of many factors. Attempts to develop a systematic psychology must, however, include understanding that the concept psychological, in the context of hierarchical conceptions of the natural order, refers to an informational domain with a particular dynamic structure and specific function. An examination of this realm reveals that concepts such as mind, consciousness, perception, cognition, affect, and personality, which have persistently remained the focus of psychological inquire over the centuries, refer to major and interrelated aspects of the psychological domain. A careful analysis of the meanings of, and interrelationships among, these concepts is intrinsic both to reducing conceptual disunity and to identifying concepts such as behavior, brain, and environment that, although important to psychological inquiry, are not in and of themselves psychological. A reduction of conceptual fragmentation will, in turn, help us distinguish between important and trivial questions, suggest important improvements in research design, facilitate information retrieval, increase the likelihood of constructing comprehensive theories, and generate much more knowledge relevant to human actions in real-world settings. The systematization of psychological inquiry will also generate the need for significant curricular changes.