L. E. J. Brouwer

Luitzen Egbertus Jan Brouwer was a Dutch mathematician and philosopher who lived from 1881 to 1966 and is regarded as one of the greatest mathematicians of the twentieth century. He established foundational results in topology, most notably the Brouwer fixed point theorem and results on the topological invariance of dimension. He also became a leading figure in intuitionism, a constructivist philosophy of mathematics that challenged David Hilbert formalism in a dispute known as the Brouwer-Hilbert controversy over the foundations of mathematical reasoning.