The challenges we face in the 21st century are global in nature. Yet it often seems like we are woefully ill-equipped to address issues such as poverty, violence, security or public health with our large-scale political institutions.

In this TED talk, Benjamin Barber suggests that we should transition away from nation states towards a system of cities, where mayors rule. Why? Because, he argues, mayors are pragmatic problem solvers who are deeply involved in the issues of the cities they serve.

They are "homies," that is, people who grew up in the city. They get things done: they are responsible for fixing potholes and educating children. In contrast, Barber notes, presidents rule abstractly and distantly, governing imagined nation states from above.

Barber argues that cities are hotspots of potential for solving the challenges that face us. Most of the issues are concentrated in cities, and these governing bodies are best equipped to collaborate and address them together. Where nation states clash, cities mesh.