David Hilbert
Notes
David Hilbert (1862–1943), German mathematician, among the most influential of the twentieth century. His 1900 list of twenty-three unsolved problems set the agenda for the century's mathematics, and his programme to place all of mathematics on a finite, consistent foundation was ended by Gödel's incompleteness theorems in 1931. The infinite hotel (Hilbert's Hotel) comes from a 1924 lecture illustrating the properties of infinite sets, and was never intended as an argument that such sets cannot exist.
Wikipedia: https://en.wikipedia.org/wiki/David_Hilbert