Synchronicity, Acausal Connection, and the Fractal Dynamics of Clinical Practice Terry Marks-Tarlow, Ph.D. a and Yakov Shapiro, M.D. b a Private Practice, Santa Monica, California, USA; b University of Alberta, Edmonton, Alberta, Canada ABSTRACT Psychoanalysts have written about synchronicity, or meaningful coin- cidence, from the beginning of the feld, yet the topic remains con- troversial and relegated to the edges of clinical work and research due to lack of a scientifc framework. This paper presents a way to con- ceptualize resonant patterning between inner and outer processes derived from the mathematics of fractal geometry. Considered the “geometry of nature” since its inception, nonlinear fractal models, methods, and metaphors reach beyond reductionism, Cartesian dual- ism, and traditional linear notions of causality to accommodate por- ous, interpenetrating boundaries between inner and outer domains as well as self-similar relational patterns. A fractal epistemology is sturdy yet fexible enough to accommodate paradox, ambiguity, uncertainty plus other complex, fuzzy processes of the ordinary analytic experi- ence. Clinical examples also illustrate that fractal framework applies more broadly to the occasional extra-ordinary experience of synchro- nicity and other “uncanny” nonlocal phenomena in clinical work. Introduction This paper focuses on synchronicity, a term coined by Carl Jung (Jung & Pauli, 1952) to indicate meaningful coincidence, or acausal correlations between psychological and physical phenomena. By highlighting synchronicity within psychoanalysis, the authors focus on edges where inner and outer, subjective and objective processes converge. We believe that both psychoanalysis and neuroscience need to move beyond a Cartesian split between Res cogitans of the mind and Res extensa of the brain and wider physical reality, which can be achieved by introducing a more nuanced way to conceive boundary conditions. This approach is now possible with the advent of Benoit Mandelbrot’s (1977) discovery of fractal patterns that exists within the nonreductive realm of non- linear dynamics and allows for fuzzy edges and infinitely deep interpenetration between seemingly disparate domains. Fractal patterns provide a holistic framework for understanding complex clinical processes and intersubjective interactions. Many psychoanalytic theorists highlight the significance of relational patterns, yet no systematic way exists to date for describing the nature of such patterning. We suggest that the self-referential, recursive fractal paradigm, including its hallmark qualities—self-similarity (the pattern of the whole repeating within the parts) and scale invariance (the pattern of the whole repeating on multiple size or time scales)—captures CONTACT Terry Marks-Tarlow, Ph.D. markstarlow@hotmail.com Private Practice, 1460 7th Street, Suite 304, Santa Monica, CA 90401. PSYCHOANALYTIC DIALOGUES 2021, VOL. 31, NO. 4, 468–486 https://doi.org/10.1080/10481885.2021.1925283 Copyright © 2021 Taylor & Francis Group, LLC