1854 – 1912
Henri Poincaré (1854–1912) was a French mathematician, theoretical physicist, and philosopher of science whose work bridged mathematics and epistemology. He is the founding figure of conventionalism in philosophy of science, arguing that scientific principles—particularly geometric axioms—are neither empirical discoveries nor a priori truths but free conventions adopted for their convenience. His philosophical writings, including Science and Hypothesis (1902), had lasting influence on logical empiricism and the philosophy of physics.
Founded conventionalism: the thesis that geometric and physical principles are conventions, not truths
Argued that the choice between Euclidean and non-Euclidean geometries is a matter of convenience, not fact
Made foundational contributions to topology, chaos theory, and celestial mechanics
Authored Science and Hypothesis, The Value of Science, and Science and Method—canonical works in philosophy of science
Anticipated key ideas in special relativity through analysis of simultaneity and the Lorentz transformations