Amartya Sen

identity can be a complicated matter. There is, of course, no great difficulty in persuading ourselves that an object is identical to itself. Wittgenstein, the great philosopher, once remarked that “there is no finer example of a useless proposition” than saying that something is identical to itself, but he went on to argue that the proposition, though completely useless, is nevertheless “connected with a certain play of the imagination.”
When we shift our attention from the notion of being identical to oneself to that of sharing an identity with others of a particular group (which is the form the idea of social identity very often takes), the complexity increases further

Indeed, the world is increasingly seen, if only implicitly, as a federation of religions or of civilizations, thereby ignoring all the other ways in which people see themselves.

Civilizational or religious partitioning of the world population yields a “solitarist” approach to human identity, which sees human beings as members of exactly one group (in this case defined by civilization or religion, in contrast with earlier reliance on nationalities and classes)