He had submitted his doctoral dissertation to the University of Berlin even before he received the offer of the teaching post, and he was allowed to move quickly to work on his habilitation thesis.
Siya ay isinumite ng doktor ang kanyang disertasyon sa Unibersidad ng Berlin kahit bago siya natanggap ang mga nag-aalok ng pagtuturo-post, at siya ay pinahihintulutan upang ilipat ang mabilis na trabaho sa kanyang habilitation sanaysay.