Gestalt theory is a broadly interdisciplinary general theory which provides a framework for a wide variety of psychological phenomena, processes, and applications. Human beings are viewed as open systems in active interaction with their environment. It is especially suited for the understanding of order and structure in psychological events, and has its origins in some orientations of Johann Wolfgang von Goethe, Ernst Mach, and particularly of Christian von Ehrenfels and the research work of Max Wertheimer, Wolfgang Köhler, Kurt Koffka, and Kurt Lewin, who opposed the elementistic approach to psychological events, associationism, behaviorism, and to psychoanalysis. The coming to power of national socialism substantially interrupted the fruitful scientific development of Gestalt theory in the German-speaking world; Koffka, Wertheimer, Köhler and Lewin emigrated, or were forced to flee, to the United States. Gestalt theory is not limited only to the concept of the Gestalt or the whole, or to the Gestalt principles of the organization of perception (as it is presented in many publications), but must be understood as essentially far broader and more encompassing: - The primacy of the phenomenal: Recognizing and taking seriously the human world of experience as the only immediately given reality, and not simply discussing it away, is a fundamental assertion of Gestalt theory, the fruitfulness of which for psychology and psychotherapy has by no means been exhausted. - It is the interaction of the individual and the situation in the sense of a dynamic field which determines experience and behavior, and not only drives (psychoanalysis, ethology) or external stimuli (behaviorism, Skinner) or static personality traits (classical personality theory). - Connections among psychological contents are more readily and more permanently created on the basis of substantive concrete relationships than by sheer repetition and reinforcement. - Thinking and problem solving are characterized by appropriate substantive organization, restructuring, and centering of the given ('insight') in the direction of the desired solution. - In memory, structures based on associative connections are elaborated and differentiated according to a tendency for optimal organization. - Cognitions which an individual cannot integrate lead to an experience of dissonance and to cognitive processes directed at reducing this dissonance. - In a supra-individual whole such as a group, there is a tendency toward specific relationships in the interaction of strengths and needs. The epistemological orientation of Gestalt theory tends to be a kind of critical realism. Methodologically, the attempt is to achieve a meaningful integration of experimental and phenomenological procedures (the experimental-phenomenological method). Crucial phenomena are examined without reduction of experimental precision. Gestalt theory is to be understood not as a static scientific position, but as a paradigm that is continuing to develop. Through developments such as the theory of the self-organization of systems, it attains major significance for many of the current concerns of psychology.