Complex Systems
A 2005 Letter to the Editor Revisited
Nearly two decades ago, I wrote a letter to the editor of Physical Therapy journal addressing a persistent issue in our profession: the gap between clinicians and scientists and its impact on clinically relevant research. The letter, published in December 2005, proposed that understanding physical therapy practice as a complex system might offer a path forward. Reflecting on that letter now, I see how much my thinking has evolved and how the foundational ideas I wrestled with then have influenced the development of the Clinical Inquiry Fellowship (CIF).
Revisiting the Problem
In 2005, I highlighted how physical therapy practice operates as a complex system—a web of interconnected variables, from therapist-patient interactions to environmental and social factors, all influencing outcomes. The reductionist approach of traditional science, while powerful for isolating specific variables, often fails to capture this complexity. Clinicians, immersed in the full system, often feel that research criteria exclude their patients and realities. This divergence, I argued, hinders the development of clinically relevant research and meaningful communication between scientists and clinicians.
At the time, I didn’t yet have the conceptual tools to propose robust solutions. My postdoctoral self-study of philosophy, logic, and mathematical modeling was still years away. What I had was an intuition: clinical practice demanded methods that embraced complexity, not avoided it.
Then and Now: From Intuition to Framework
Fast forward to today. The CIF is the embodiment of my efforts to address the very issues raised in that letter. The key shift has been moving from intuition to a structured framework grounded in knowledge-based practice (KBP) and causal models:
“Complex” Systems Thinking: The CIF teaches fellows to appreciate the dynamic, interconnected nature of clinical practice, emphasizing that "the whole is more than the sum of its parts." And my understanding of “complex” has also changed, seeing it more as an epistemological problem, not an ontological problem. Ontology (the nature of being) presents us with “systems” in reality. Epistemology (theory of knowledge and methods of knowing), and in particular limitations in our ability to know, presents us with “complex systems” because of the limitations (exacerbated by an empiricism burdened by logical positivism) of the methods of knowing. In other words, what exists are “systems”, but how we see them and try to know them compels someto add the word “complex”.
Causal Models: Through directed acyclic graphs (DAGs), we now have a tool to explicitly map and analyze systems. DAGs allow us to visualize the relationships among variables, hypothesize about causality, and incorporate new evidence iteratively.
Critical Realism: As an epistemological foundation, critical realism acknowledges the imperfection of our knowledge but insists on its practical utility. It guides the CIF’s approach to integrating evidence with reasoning in a way that respects the complexity of clinical practice.
What Has Changed?
Back in 2005, I suggested that the methods of complex systems science could help improve the relevance of clinical research in physical therapy. Today, I have a clearer vision of how to achieve this, but the vision is still incomplete. The CIF equips physical therapists to move beyond the reductionist paradigm. By engaging with systems through causal modeling and critical reasoning, fellows gain the tools to bridge the gap between research and practice and contribute to continued development of the approach.
Why This Matters
The issues I wrote about in 2005 persist today. Clinicians still wrestle with the divergence between research findings and practical realities. Scientists still struggle to design studies that reflect the messy, interconnected nature of real-world practice. The CIF addresses these challenges head-on by fostering a community of scholars committed to rethinking clinical inquiry.
Looking Ahead
In future posts, I’ll revisit specific points from my 2005 letter and explore how KBP and the CIF’s methods address them. My hope is that this ongoing dialogue will inspire others to join us in redefining clinical reasoning and research in physical therapy.
Call to Action
If you’re ready to think deeply about the complexities of practice and contribute to the evolution of clinical inquiry, I invite you to explore the Clinical Inquiry Fellowship. Together, we can build a future where physical therapy research and practice are seamlessly connected.