Nancy Cartwright

Nancy Cartwright (born 1944) is a philosopher of science whose work challenges the assumption that fundamental physical laws govern the actual world in the way they govern idealized models. Her central thesis, developed in How the Laws of Physics Lie (1983) and The Dappled World (1999), is that scientific laws are not universal truths about nature but tools that work in carefully prepared contexts — 'nomological machines' that require specific conditions to operate.

Cartwright's work has direct implications for medicine and the social sciences. If physical laws are already ceteris paribus, then biological and social generalizations are even more context-dependent. The search for 'what works' in policy or therapy cannot be answered by finding universal laws but by understanding the 'capacity' of interventions to produce effects in specific kinds of situations — a framework she calls 'causal inference from messy data.'

Her critique of unity-of-science reductionism makes her a natural ally of complexity science and a critic of the assumption that RCTs, by controlling for context, reveal causal truths that transfer across situations. For Cartwright, the controlled trial does not eliminate context-dependence; it substitutes one context (the trial) for another (the clinic), and the transfer between them is never guaranteed.