Professor Kwame Anthony Appiah is a philosopher advocating a school of thought called 'cosmopolitanism'.
He describes cosmopolitanism as a very old tradition because the word "cosmopolitan" comes from the Greek phrase from the 4th century BC, 'kosmopolites', which means "citizen of the world".
It is a tradition of thought, which tries to develop a metaphor for the idea that we are all citizens of the world, he explains.
Cosmopolitans welcome diversity of culture, race, religion and nationality. Amongst other things, Appiah talks about the backlash to cosmopolitanism in places like Europe where economic hardship has led to an increase in nationalism, an anti-immigrant sentiment and the election of conservative politicians.
He also makes some interesting remarks about cosmopolitanism and the suppression of human rights in China.