Emil Leon Post

Emil Leon Post (February 11, 1897 – April 21, 1954) was an American mathematician and logician of Polish-Jewish descent. Born in Augustów, Congress Poland, he immigrated to New York City with his family in 1904. A childhood accident led to the loss of his left arm, which influenced his career choice towards mathematics instead of astronomy. Post earned his B.S. from the City College of New York in 1917 and his Ph.D. from Columbia University in 1920. He pursued post-doctoral studies at Princeton University. Post is celebrated for his pioneering work in computability theory, independently developing a computational model similar to the Turing machine, known as Formulation 1 or the Post–Turing machine. He introduced the Post correspondence problem, a significant example of an undecidable problem, which had profound implications for formal languages and theoretical computer science. Post also contributed to recursion theory, developing the concept of Post canonical systems and investigating computability and decidability. His doctoral thesis, published in 1921, proved the completeness of the propositional calculus of Principia Mathematica and utilized truth tables. He nearly discovered Gödel's incompleteness theorems. In addition to his theoretical work, Post made contributions to the theory of polyadic groups. He faced personal struggles with mental health, including manic attacks and depression, which led to a doctor's advice to limit his research time. Post died in New York City in 1954 from a heart attack.