How is Gestalt Therapy defined? How does it grow theoretically?
I don't mind "thinking out loud" about that. Perhaps we can get something going.
Defining it depends upon which manifestation you want to examine. There's Gestalt therapy based on the constructs most familiar to Gerhard Stemberger, Thomas Fuchs, and Hans-Juergen Walter, and these would be the applications coming from theoretical Gestalt psychotherapy (personally, I'm interested to hear how they would define that manifestation of Gestalt). There's the Gestalt therapy of Fritz Perls, but even that has periods of emphasis such that it seems to be very different in character in its early expression as compared to today. Leslie Greenberg, for instance, made a distinction between the Gestalt that he learned early on and the Gestalt that is practiced today. The early manifestation he described has much more of a radical individualism, while today Gestalt has come into what he called its "dialogical phase." I've read descriptions of Gestalt that sounded as if the authors had seen Fritz with Gloria, read the Gestalt prayer, and drew a cartoon of the therapy. That's not remotely the practice I've observed in contemporary Gestalt therapists like Todd Burley and Lynne Jacobs. I've read the defining statements of Gestalt by Gary Yontef and Robert Resnick, and I've talked with Les Greenberg about it; at this point I settle on the following:
To me Gestalt is defined by several costructs. First is an appreciation for the field, which is all that bears upon an individual, including his or her development, the cultural milieu, and his or her intimate systems. Second, is respect for phenomenological process, which includes the neurophysiological base from which a construction of meaning out of experience can take place (in this respect I am fascinated, for instance, in the possibilities of considering body memories and emotional memory in general, as described in the work of Joseph LeDoux, where these things are processed first sub-cortically, and then made sense of, delt with by the cortex). Third, is the dialogical relationship, including an appreciation for the manner in which people support themselves in contact, an understanding of the difference between I-Thou and I-It, and the cycle of experience itself (this, along with the phenomenological, is the context for the formation and satisfaction of figures). Fourth, is the use of experiment, which accepts a behavioristic aspect into the therapy, but not in a determinist, overcontrolled fashion; rather, experiment is the means by which new information facilitates awareness. Fifth, is appreciation for the paradoxical nature of change - people can best change by supporting the present experience of self.
Gestalt shares many of these constructs with other therapies. For instance, as Greenberg points out, the client-centered approach has its version of dialogue, but lacks the experimental, something that when added, distinguishes Gestalt from the Rogerian approach. This, then, serves as a model for distinguishing Gestalt from still other psychotherapies that may have aspects similar or in common with Gestalt. It is not that Gestalt has these certain characteristics, but that it has all of them.
This leads to the question of how Gestalt is to grow, and the answer is that it is to grow by virtue of assimilation. This is not merely grafting bits and pieces of other systems, or by finding similarities between Gestalt and other therapies, but by truly embracing, considering, and "chewing" on these other approaches, keeping that which truly fits. Thus, a dialectic occurs in which that which is assimilated becomes synthesized, changed to reflect a truly Gestalt version of the construct, and Gesalt theory itself grows to make space for this new piece. Because of this process of assimilation, Gestalt practitioners need to be open to investigating new things, even in unlikely places. As Joe Wysong says, they need to be able to "spit out" what is not capable of being assimilated, but this is not the same as spitting out what merely doesn't look like Gestalt therapy. Such a thing would be like introjecting in reverse, and no one can grow if they keep spitting up their food. Gestalt therapy will not grow if it merely tries to stay the same, constantly checking for what looks, feels, and tastes like what the forfathers said Gestalt was like.