[1][2][3] Through holism, "a person's thinking, feeling, actions, perceptions, attitudes and logical operations"[4] are seen as one unity.
Walter, a student of Gestalt psychologist Friedrich Hoeth, was influenced to form the core of his theoretical concept on the basis of the work of Gestalt theorists Max Wertheimer, Wolfgang Köhler, Kurt Koffka, Kurt Lewin, and Wolfgang Metzger.
The majority of the extensive literature on Gestalt theoretical psychotherapy which has been published in the decades since then is in the German language.
Gestalt Theoretical Psychotherapy in this form has gained popularity predominately in German speaking countries.
Wolfgang Metzger and Paul Tholey identify five sub-approaches of the Gestalt Theory, which, relating to each other, form up an organized system.
The Gestalt theoretical psychotherapy therapeutic process is a relationship between two individuals in which both the therapist and client develop an egalitarian attitude.
The therapist should act as a “fellow voyager”[11] of the client, supporting them in discovering their specific and personal feelings and problems.
Stemberger points out that whatever one discovers relates to “not only to what is descriptively encountered in the experience, such as what is seen, heard, felt, and sensed, but also to what is thought, imagined, remembered, and planned.”[12] Referring to Kurt Lewin, a change can only arise if the therapist raises full awareness to the “dynamic properties”[13] of the client's current psychological situation.
[13] The client directs his overall attention to the presence, listening inside themselves, remaining conscious, following whatever appears in the current state.
[15] Whatever one hypothesizes, says, or establishes about the trans-phenomenal world comes from interpreting data acquired using phenomenal methods, theoretical forms and models.
The data obtained constitutes the “critical-phenomenal view,” through which each individual has their own “microcosmic phenomenal world” seen by them as reality.
[10] Köhler, recognizing the contributions of Wertheimer and Koffka, designed the “isomorphism assumption,” suggesting a uniformity between physical and physiological operations and psychological processes.
[10] Critical realism suggests that phenomenal worlds of individuals vary and different experiences arise.
"[10] For that reason, GTP should evaluate the extent to which beliefs and theories may affect the client's perception, a judgement of the experience, and behaviour.