A lecture invitation put Alfred Tarski on the last ship from Poland
In August 1939 the logician Alfred Tarski sailed for a congress at Harvard on what proved the final ship from Poland to America before the invasion. He went reluctantly, leaving his wife and children behind, and would not see them again until 1946. Most of his Jewish relatives did not survive the war.
He was born Alfred Teitelbaum in Warsaw on 14 January 1901, to comfortably off Polish-Jewish parents, and entered the University of Warsaw in 1918 to study biology. The university was fast becoming a world centre for logic, and Stanisław Leśniewski persuaded him to switch to mathematics. In 1924 Tarski became the youngest person to earn a Warsaw doctorate, and the only student Leśniewski ever supervised; the two later cooled over Leśniewski's growing anti-semitism. In 1923 he and his brother had taken the surname Tarski and converted to Catholicism, though Alfred was an avowed atheist.
University posts paid poorly, so for years he supported himself teaching mathematics at a Warsaw secondary school while producing groundbreaking papers. Prejudice blocked his path: in 1937 Poznań University abolished a chair rather than give it to him, by far the best candidate, because he was Jewish. His ties to the Unity of Science movement, which grew out of the Vienna Circle, brought the Harvard invitation that saved his life.
From 1942 he taught at Berkeley, becoming a citizen in 1945 and supervising 24 doctorates, among them Julia Robinson and Solomon Feferman. His seminars were legendary for demanding total clarity; some students fled, while a loyal circle became leaders in logic. He was unusually encouraging to women for his era, with five women among his doctoral students, though his conduct toward some of them was far from blameless.
His range was vast; his collected papers fill about 2,500 pages. With Stefan Banach in 1924 he proved that, if the axiom of choice is accepted, a solid ball can be sliced into finitely many parts and reassembled into two balls each as large as the first. He showed that the first-order theory of real-number arithmetic is decidable, surprising given that ordinary whole-number arithmetic is not, and gave a lean set of axioms for plane geometry. His biographers rank him beside Kurt Gödel as a transformer of twentieth-century logic, especially on truth and models. He died in 1983.
Source: Alfred Tarski
