Biology and panpsychism: German evolutionists and a philosopher Theodor Ziehen (1862–1950)

Abstract

Theodor Ziehen was a prominent German psychiatrist and psychologist and a marginal philosopher of the first half of the 20th century who developed an exotic subjective-idealistic theory based on quasi-empirical psychological arguments. Although Ziehen was seen by contemporaries (most prominently by Vladimir Lenin) as a representative of the same philosophical current (empirio-criticism) as Mach and Avenarius, he never achieved their prominence in the history of philosophy. At the same time, Ziehen’s philosophy became influential in German biology, first of all, due to his direct and very strong impact on Bernhard Rensch. Rensch, in his turn, was the most significant figure on the international scene of what is known as the Modern Evolutionary Synthesis in biology. Rensch was not the only biologist influenced by Ziehen’s ideas. Ziehen had some communication with the “German Darwin” Ernst Haeckel and played a prominent role in the concept of the founder of biological systematics Willi Hennig. How to explain Ziehen’s prominent place in the history of evolutionary biology, despite his obscurity in the history of philosophy? Our hypothesis is that Ziehen became a visible figure in evolutionary theory because of the monistic bias in German biology. Ziehen’s epistemology appeared to be compatible with evolutionary monism and was developed by a practicing psychiatrist therefore obtaining a character of a quasi-experimental doctrine.