We live in a complex and unequal world, a world without historical precedent. During the last two million years, successive human species have colonized the planet, and during the last ﬁve decades our species has begun the physical exploration of space. In the course of human history, the decisions which affect us have been taken at increasing distances from our daily lives: autonomy has been surrendered to, and power appropriated by, regional and national governments. Out of the ﬁrst states ﬁve and a half thousand years ago grew the ﬁrst empires, mobilizing and exploiting human labour and material goods across regions many times the size of the original states. From the ﬁfteenth century ad, European colonists annexed land and peoples on other continents. As recently as the 1950s our world atlases were a collage of colours, symbolizing the empires of European nation states. The leaders of these states took political decisions affecting the lives of millions around the globe, and fought two world wars in the last century. Capitalism accentuated inequalities, both within nation states and between those states and their colonies. Although we now live, with the exception of a few enclaves, islands and promontories, in a post-colonial world, changes in technology, politics, culture and the economy mean that our lives are governed increasingly at the global scale.