Wolfgang Pauli received his habilitation from the University of Hamburg in 1924  – the same year he discovered his Nobel-Prize-winning exclusion principle – and delivered his inaugural lecture on 23 February. He was awarded the title of professor in 1926, then obtained a professorship in theoretical physics at the ETH, Zürich, in 1928. His tendency to forget about the audience, and think out problems as he went along, proved challenging for some students. But, as Markus Fierz pointed, they at least learned to think critically about a theory!