David Hilbert

David Hilbert (1862-1943) was a German mathematician who attempted to formalize mathematics in a methodical manner. He is most famous for listing the 23 greatest unsolved problems of mathematics in the early 1900s, problems that included the Riemann hypothesis, the continuum hypothesis, Goldbach's conjecture, the well ordering of the reals, the transcendence of powers of algebraic numbers and the extension of Dirichlet's principle, in addition to his analogy for Cantorian infinite sets, known as 'Hilbert's Hotel'.

Later, after Hilbert did work in algebraic number theory and geometry, and created the "Hilbert space," he was an early promoter of the general theory of relativity. In 1934 and 1939 he published two works attempting to develop a "proof theory," which is a direct check for the consistency of mathematics. But in 1931 Kurt Godel had already proved that this goal was impossible.