In the fall of 1935 Pais began his studies at the University of Amsterdam without a clear idea regarding his desired career. With an interest in the exact sciences, he gradually gravitated to chemistry and physics as major subjects, and mathematics and astronomy as minor subjects. In the winter of 1936/1937 his career goals were defined by two guest lectures by George Uhlenbeck, professor of theoretical physics at University of Utrecht. Pais was fascinated by Uhlenbeck's discussion of Enrico Fermi's incorporation of the neutrino into the theory of beta radiation.