Numerous geographers writing in recent years concerning the nature and scope of their subject have described the relation of their field to other fields of science in terms of a concept said to stem from Immanuel Kant and from Alexander von Humboldt. Whatever may be the original source of the concept, its importance in the current geographic thought stems from the writing of Alfred Hettner, the German master of the methodology of geography.

Hartshorne (1958) "The concept of geography as a science of space, from Kant and Humboldt to Hettner" in: Annals of the Association of American Geographers Vol 48 (2). p. 97