Beyond outcome studies: Good psychotherapy rests on many secure epistemic foundations

This article argues the thesis that rigorous, strongly reasoned psychotherapeutic practice rests, not only (and not always) on outcome research, but on many further equally, and in some cases more, secure epistemic foundations. In part 1 of the article, based on currently well-established epistemological thinking, a ranking of the degree of certainty of propositions yielded by different knowledge sources, and thus the confidence with which we may believe and act upon them, is presented. Following the description of each knowledge source, an analysis of the degree to which it enters into the practice of psychotherapy is developed. In part 2, several further knowledge sources essential to psychotherapy that are difficult to rank are presented, as well as the confidence that can reasonably be placed in knowledge derived from these sources. In part 3, an individual therapy session conducted by Aaron Beck is analyzed to illustrate its utilization of many of the knowledge sources discussed in the article. •Psychotherapeutic practice rests, not only on outcome research, but on many further secure epistemic foundations.•The core procedural principles of our major schools of therapy rest on logical, not empirical, foundations.•Rigorous clinical thinking embodies the correct application of valid pre-empirical logical forms of inference.•Direct, first-hand observation is the most certain knowledge therapists have about their clients.•Few empirically supported treatments have demonstrated consistently strong research support.•Under the right conditions, information gleaned from client self-reports warrants high levels of belief.