 This is an extension into the realm of the understanding of human beings of Kant’s ‘Copernican’ revolution (to use Kant’s own epithet). Kant gave full recognition, for the first time, to the inescapable contribution made by our minds to grasping the non-human world; Berlin mirrors this move with a scarcely less fundamental claim of his own, that there are equally inescapable ways in which, at any given time or at all times known to us, we cannot but think of and understand the behaviour and experience of our own kind.