Uexküllian Umwelt as science and as ideology: the light and the dark side of a concept.

The concept of Umwelt, in particular the interpretation originally developed by Jakob von Uexküll, played an important role in the development of biological thought of the first half of the twentieth century. The theory of Umwelt (Umweltlehre) was one of the most original ideas that appeared in German biology at that time. It was the first attempt to introduce subjectivity into a science about organisms; it laid down the foundations of behavioural research and inspired the development of ethology. However, the theory of Umwelt has also been used to support more sinister activities and even some dangerous ideologies. The concept of Umwelt is of interest not only to historians: within some intellectual circles, it is still broadly used today. Our aim was to analyse the notion's historic development within the context of biological thought of the first half of the 20th century. In particular, we focus (1) on how the concept was adopted and adapted for various, often widely diverging purposes; (2) on interactions between the Umweltlehre and other contemporary worldviews. We argue that in order to understand the developments that occurred in twentieth century biology, one needs to properly appreciate the role which Umweltlehre played in these. Even more importantly, the Umweltlehre is a worldview that influenced not only science but also politics and social affairs. In this respect it functioned rather like a number of other scientific and ideological frameworks of that time, such as Synthetic Darwinism.