you gotta believe in yourself

L. E. J. Brouwer (Luitzen Egbertus Jan, 1881-1966) was a Dutch mathematician and the founder of intuitionism, a philosophy which admits only things that can be constructed by finitary means. In particular, intuitionism does not accept the validity of the Law of the Excluded Middle, nor the Axiom of Choice. Ironically, Brouwer is best known (outside the philosophy of mathematics) for his fixed-point theorem, which he proved by means of conventional (non-constructive) analysis, i.e., techniques that he philosophically considered to be questionable if not downright invalid.