Following his time with Müller, he returned to Leipzig to study under Wundt as his assistant in the autumn of 1886. On 12 October 1887 Külpe was awarded his PhD. He titled his thesis “Zur Theorie der sinnlichen Gefühle”, or in English, The Theory of Sensual Feeling. This is a topic that Külpe was interested in over the course of his life, and especially influenced his later studies and lectures on esthetics. He then became Privatdozent at the University of Leipzig, before being promoted to a professorship extraordinarius in 1894. In October 1894, he attended Würzburg as professor ordinarius, the highest obtainable rank as a professor at a German university, for both philosophy and esthetics. It was here in 1896 that Külpe founded a psychological laboratory. He was able to increase the size and improve the equipment until the Würzburg laboratory became the most outstanding institute of psychology in Germany aside from Leipzig. Here, he trained numerous influential psychologists including the likes of Max Wertheimer, Kaspar Ach, and Henry Watt.