 For the next four years, Fechner devoted himself to Naturphilosophie. Although he said that he little understood Oken’s book, of which he read only the first chapter, he went on to read other Naturphilosophen, especially Schelling and Steffens. He was indeed so involved in Naturphilosophie that in 1823 he wrote his PhD dissertation on it, Praemissae ad theoriam organismi generalem (a summary is provided by Marilyn Marshall 1974b), which was a general theory of organisms. In 1824, in a collection of essays, Stapelia mixta, he made his own proposals for the method of Naturphilosophie  (1824).[4] 