1928 – 1990
John Stewart Bell (1928–1990) was a Northern Irish physicist and philosopher of physics whose foundational work on quantum mechanics reshaped debates about locality, realism, and hidden variable theories. Best known for Bell's theorem and the associated inequalities, he demonstrated that no local hidden variable theory can reproduce all the predictions of quantum mechanics. His work transformed abstract philosophical questions about the EPR paradox into empirically testable claims.
Proved Bell's theorem (1964), establishing limits on local hidden variable theories
Derived Bell inequalities, enabling experimental tests of quantum non-locality
Revived and rigorized debate on the EPR paradox and quantum completeness
Championed Bohmian mechanics as a coherent alternative to Copenhagen interpretation
Authored Speakable and Unspeakable in Quantum Mechanics, a landmark collection on quantum foundations