Acceptance and Commitment Therapy's Philosophical Foundation under Scrutiny: An In-Depth Discussion of A-Ontology

Standard view in scienceBroadly speaking, science is a structured approach to reality, growing from methodologically rigorous research, and resulting in knowledge organized in a system. Thus, simply said, scientific knowledge results from the research of reality - regardless of how one defines it. What aspect of reality is researched depends on the problems we have. The problems could be theoretical and/or practical. Typically, the theoretical problems are approached by fundamental/basic/exploratory research, while the practical problems are approached by practical/development/innovation research. Translational research is a particular type of practical research aiming to solve practical problems based on the already existing outcomes of the fundamental/basic/exploratory research. In sum, in science we try to generate knowledge by rigorous research, in order to solve theoretical and/or practical problems (David, 2006, 2007). Any scientific system (including psychotherapy) has three main components: (1) philosophical assumptions, (2) theories, and (3) models (see Eysenck & Keane, 1990). We will briefly discuss each of these components below.Philosophical assumptions are fundamental ideas providing the very foundation of any scientific system. Indeed, a scientific paradigm is a "universally recognized scientific achievements that, for a time, provide model problems and solutions for a community of practitioners. " (Kuhn,1996, pg. 10). They are not judged as being true or false, but rather they are simply accepted on the basis of their utility (Kuhn, 1962) (i.e., the degree to which they can generate powerful knowledge organized in theories and models). They precede and condition the collection of empirical evidence, underlying the theories and the models. In sum, the philosophical assumptions are the landmarks that delineate the view of reality, guiding the organizing and the understanding of reality (e.g., "worldviews"; Pepper, 1942). Therefore, philosophical assumptions underpinning scientific systems guide the development of knowledge through research. They can refer to the nature of (1) things/existence/reality (e.g., Which entities are real? ; ontological assumptions), or world nature, more generally (e.g., Is there any reality independent of the mind? ; metaphysical assumptions), (2) knowledge (e.g., Is this knowledge true or false? ; epistemological assumptions), or (3) values (e.g., How valuable is this approach? ; axiological assumptions). Theories are structured explanations/interpretations of the facts derived from philosophical assumptions. They can (and should be) judged as being right or wrong, true or false, using scientific inquiry methods (i.e., the values of truth). Theories have several functions (see David, 2007): (1) description of reality (i.e., which are the dimensions/components of reality and how they are related); (2) explanation of reality (i.e., how phenomena occur); (3) prediction/control of reality (i.e., what we should expect/what is likely to happen); and (4) organization of knowledge about reality.Models come from applying a theory to a specific situation/case. Therefore, a model is anything used as a representation of a theory. Sometimes the model is discovered first and the theory is developed based on it, other times the theory is devised first and the model is later revealed as a particular case of the theory. Either way, a model will always behave as a prototype of the theory (see David, 2007). Both theories and models should undergo testing, in order to judge them as true or false. There are three main approaches to test theories and models. First of them, verifiability, is based on the original positivism (Compte, 1830) and logical positivism (Carnap, 1937) approaches. To be verifiable, a theory/model must be reducible to observable propositions whose truth value is determined by directly confronting the propositions with perceptual/observable data. …