Imagine: a physician prescribes a drug to a patient, and in the following weeks or months the patient’s symptoms change; perhaps they improve. The patient might think “the drug worked for me”, and the physician might infer that too. Are such inferences reliable? The evidence-based medicine movement says no: first-person anecdotes and clinical expertise are unreliable forms of evidence when evaluating the general effectiveness of drugs, says evidence-based medicine. Yet some physicians and philosophers support such appeals to first-person experience, and people very often make the worked-for-me inference. We develop a formal model and simulate causal inference based on clinical experience. We conclude that in very particular clinical scenarios such inference can be reliable, while in many other routine clinical scenarios such inferences are not reliable. Specifically, if diseases are at least moderately placebo-responsive or have at least a moderate natural course of improvement, then worked-for-me inferences are unreliable. Such inferences are particularly problematic, then, for psychiatry.

Jacob Stegenga is a Professor in the Department of History and Philosophy of Science at the University of Cambridge. He has published widely on fundamental topics in reasoning and rationality and philosophical problems in medicine and biology. Prior to joining Cambridge he taught in the United States and Canada, and he received his PhD from the University of California San Diego. He is the author of Medical Nihilism and Care and Cure: An Introduction to Philosophy of Medicine, and he is currently writing a book tentatively titled Heart of Science.

Jacob runs the YouTube channel PhiSci: Conversations about Philosophy and Science, where he interviews some of the world’s most prominent philosophers and scientists about a wide range of topics.

Talk chaired by:  Lisa Cosgrove

Watch a recording of: Prof Jacob Stegenga’s presentation