A Return to Functional Analysis, the Search for Mechanisms of Change, and the Nomothetic

In this invited commentary, I provide an historical and conceptual context for “The Future of Intervention Science: Process-Based Therapy” by Stefan Hofmann and Steven Hayes (this issue, p. 37). Special attention is paid to the importance of change mechanisms in psychological intervention, the use of functional analysis instead of categorical schemes such as the Diagnostic and Statistical Manual of Mental Disorders and treatment manuals in randomized clinical trials, and the challenge of applying nomothetic principles to individual cases. Historical context is provided for prior examination of these core issues in numerous articles and books extending back for over 60 years