George Bergman · CC BY-SA 4.0

Redefined what it means for a mathematical statement to be true, developing a formal theory of truth for logical languages that became foundational to model theory. Trained in Warsaw's influential school of logic, he emigrated to the United States in 1939 and spent the rest of his career at UC Berkeley. His biographers rank him alongside his contemporary Kurt Gödel as one of the two logicians who most reshaped twentieth-century mathematical logic.