Kurt Gödel changed the understanding of mathematics. His two incompleteness theorems, formulated in 1931, used formal logic to reveal the fragility of the foundation of the great edifice of mathematics that had been painstakingly built since the time of Euclid. The scientific community was forced to admit that the validity of a particular hypothesis may lie beyond any rational attempt to prove it, and intuition cannot be excluded from the realm of mathematics. Gödel, educated in prosperous interwar Vienna, quickly became interested in epistemology and the theory of evidence. Like his friend Albert Einstein, he challenged the dogmas of modern science, and in the same way, war and exile were present in his life.