Immanuel Kant is best known to us as a systematic metaphysician who defended the a priori status of both the principle of morality and the fundamental principles of a science of nature. It may therefore come as a surprise to learn that as a university teacher, Kant's most frequently offered and most popular courses had to do with empirical materials to which he had difficulty giving any systematic form. These were lectures on what Kant called the two kinds of “world-cognitions” (Welterkenntnisse): physical geography and anthropology (VPG 9:157, ApH 7:122n, RM 2:443). Both deal with the environment in which human beings live and act, the former with the outer, natural environment, the latter with both the constitution of the human soul and the social and historical environment in which human beings, both individually and collectively, shape their own nature as rational creatures. Both of these empirical sciences were new in Kant's time, and he could even claim to share in their invention.
Kant began his academic career as a natural scientist, whose special interest in geology and earth sciences is clear from his early treatise Universal Natural History and Theory of the Heavens (1755). In this work he proposed the earliest version of the nebular hypothesis of the origins of the solar system (though the hypothesis became well known only after its later and more mathematically sophisticated presentation by La Place). For most of the previous decade, Kant had been writing treatises on physics, astronomy, and geology, discussing such subjects as earthquakes and questions of meteorology. He began lecturing on physical geography in 1756, offering the same course on a more or less regular basis during the summer semester. His interest in anthropology, or at least one side of it, appears to have grown out of this, insofar as Kant sought to “display the inclinations of human beings as they grow out of the particular region in which they live” (Ak 2:9). It was for this reason that Wilhelm Dilthey argued that Kant's interest in anthropology should be fundamentally understood as arising out of his interest in physical anthropology – focusing, however, not on the natural environment as such but on human beings’ activities in it.