Events in Ukraine and the forthcoming referendum in Scotland have focused attention on deeply felt ideas of nationalism and national sovereignty.
Here, Professor David Cannadine dispatches a few myths about nation states - arguing that they a relatively modern inventions and that, in part, the loyalty we owe them was a carefully constructed political strategy.
He looks at the ways in which nationalism reached a peak at the time of WW1 and how the artificially created states that emerged after the War were inevitably flawed.
He also asks questions about whether, in a globalised world, we couldn't do better in terms of governance - either by looking to collections of cities or to groupings of nations to solve the problems of the 21st century.
Producer: Susan Marling
A Just Radio production for BBC Radio 4.