The cosmopolitan turn in democratic
political theory can be regarded as a radical
extension of Kant’s theory of world citizenship
which, as noted earlier, revolved
around the duty of hospitality to strangers.
One might regard it as a necessary extension
of his claim that the ‘touchstone’ for deciding
whether or not something is true is the
possibility of ‘testing (upon) the understanding
of others whether those grounds of the
judgment which are valid for us have the
same effect on the reason of others’ (quoted
by McCarthy, 1997: 211).