 During this time, he contracted a prolonged illness, which continued until the end of the summer of 1917.In October 1917 he enrolled in the University of Berlin to study philosophy and broke off his studies at the end of 1918.In Berlin, Ehrlich attended lectures by professors Ernst Cassirer, Max Dessoir, Benno Erdmann, Alois Riehl, Friedrich Julius Schmidt and Ernst Troeltsch.