Moses Schönfinkel
Moses Ilyich Schönfinkel, also known as Moisei Isai'evich Sheinfinkel' (; 29 September 1888 – 1942), was a Russian logician and mathematician, known for the invention of combinatory logic. Life. Schönfinkel attended the Novorossiysk University of Odessa, studying mathematics under Samuil Osipovich Shatunovskii (1859–1929), who worked in geometry and the foundations of mathematics. From 1914 to 1924, Schönfinkel was a member of David Hilbert's group at the University of Göttingen in Germany. On 7 December 1920 he delivered a talk entitled "Elemente der Logik" ("Elements of Logic") to the group where he outlined the concept of combinatory logic. Heinrich Behmann , a member of Hilbert's group, later revised the text and published it in 1924. In 1928, Schönfinkel had one other paper published, on special cases of the decision problem ("Entscheidungsproblem"), that was prepared by Paul Bernays. After he left Göttingen, Schönfinkel returned to Moscow. By 1927 he was reported to be mentally ill and in a sanatorium. His later life was spent in poverty, and he died in Moscow some time in 1942. His papers were burned by his neighbors for heating. Work. Schönfinkel developed a formal system that avoided the use of bound variables. His system was essentially  equivalent to a combinatory logic based upon the combinators B, C, I, K, S and a combinator for a universally quantified nand function which he called U. Schönfinkel stated that the system could be reduced to just K, S, and U (a colleague stated that U could be factored to the end of any expression and thus not always explicitly written) and outlined a proof that a version of this system had the same power as predicate logic. His paper also showed that functions of two or more arguments could be replaced by functions taking a single argument. This replacement  mechanism simplifies work in both combinatory logic and lambda calculus and would later be called currying, after Haskell Curry. While Curry attributed the concept to Schönfinkel, it had already been used by Frege (an example of Stigler's law). The complete known published output of Schönfinkel consists of just two papers: his 1924 "On the Building Blocks of Mathematical Logic", and another, 31-page paper written in 1927 and published 1928, coauthored with Paul Bernays, entitled "Zum Entscheidungsproblem der mathematischen Logik" ("On the Decision Problem of Mathematical Logic").