  Krull's Fundamentalsatz, the generalisation of the main theorem of elementary
number theory to integral domains, is the starting point of Lorenzen's career
in mathematics. This article traces a conceptual history of Lorenzen's
successive reformulations of the Fundamentalsatz on the basis of excerpts of
his articles. An edition of the extant correspondence of Lorenzen with Hasse,
Krull, and Aubert provides a better understanding of the context of these
investigations.
