In Kant and Modern Political Philosophy, Katrin
Flikschuh argues that the original common possession of the
earth, and in particular the limited spherical character of the
earth (der Erdkugel), plays a much more fundamental role in
Kant’s justification in cosmopolitan right than I am claiming
that it does. Flikschuh’s argument is worth considering in some
detail. Flikschuh bases this reading not on Kant’s “Perpetual
Peace” essay but on his Rechtslehre, the first half of Die Metaphysik
der Sitten (The Metaphysics of Morals). Two passages are
of special relevance here: