English: The emergence of the term Umwelt within twentieth-century biological thought is reminiscent of the turn towards the “subject” in early modern philosophy. The term Umwelt originally had a spatial connotation, which explains why analysis reveals an interdisciplinary terminological connectedness transcending the confines of any specific scientific discipline. This interdisciplinary consideration opens the way for systematic perspectives developed against the relevant historical background, in particular the Umweltlehre of Jakob von Uexküll, who explicitly introduced the notion of a “subject” into biological research. His contribution is assessed in terms of multivocal spatial terms such as (bio-)milieu and (bio)-sphere and the subject-object relations found in nature (within the plant and animal realms). This highlights the inherent limitations of the Umwelt concept, also explaining why in its purely biological sense it cannot be applied to the domain of human experience.