Abstract
In this historical treatise two biological‐system theories, formulated in the 1920s and 1930s, are roughly sketched. The first part discusses the concept of a thermodynamically open system, as coined by the Russian pathologist Ervin Bauer (1890–1942). Like Bertalanffy, Bauer wanted to prove the specificity of the biological sciences against physics. To achieve this, he postulated the necessity to formulate specific laws of motion which are valid for living matter alone. In the second part of the paper, the organismic‐system theory of the Austrian‐Canadian philosopher and biologist Ludwig von Bertalanffy (1901–1972) is outlined. The focus of this theory relied on the process dynamics that is inherent inside an organismic system. Both theories exemplify closure models for a living organism from a methodical point of view that distinguishes these earlier models from semantic closure, developed by Howard Pattee as an epistemic clue in solving the enigma of living phenomena. The objective here is to disclose the essential differences between these closure conceptions. To encourage further research on closure, the essay concludes with a few questions concerning clarification of the term.