Inbreeding

It is completely illogical that we have borders to restrict people from moving. The result is that people from the same country mostly stay put and breed strange ideas among themselves - often ideas which foreigners are very quick to recognise as silly.

The effect is the same as when people from a small village only marry each other, or when the royal houses of Europe did so. The result is that defects are magnified.

There is nothing wrong with the idea of borders, of course. But they should be used the opposite way round. At birth, every human should be given a passport. After the age of twenty, each human should be prevented from ever again going back to the country where he was born.

That's the only way to make sure we share the rich experiences of all the world's cultures.