The philosopher Immanuel Kant once said that if the world were an infinite plane, then all the problems of political philosophy would be solved. If one citizen disagreed with the way his society were run, he could pack up and start a new one over there. In reality, we’re stuck with this spherical earth, and if you keep re-locating over there, eventually you’ll end up back here, to face whatever it is you were trying to get away from in the first place. So it looks like we’re stuck with each other, and the challenge of modern society is to find a compromise.

One thing Kant probably didn’t imagine is that in the 21st century, we would spot an opportunity for a new over there. Last week was the third annual conference on Seasteading. The Seasteading movement aims to create small floating cities in international waters. They envision experimental societies, intentionally-formed communities free from the regulation of national governments and the influence of social mores.

In reality, the most serious interest in seasteading has come from rich venture capitalists. Peter Thiel, the billionaire founder of paypal and noted libertarian, donated $500,000 to the Seasteading Institute in 2005. As a Silicon Valley venture capitalist, Thiel knows first-hand the downsides of government regulation. Thiel has seed-funded a Seastead off the shore of California, which will provide day trips to the mainland and promises to get around the restrictive work visa system, allowing the unrestricted flow of international capital and labour.

But for some, seasteading is more than just a legal hack. It’s an opportunity to apply the scientific method to society; each seastead an experiment to test an economic or political idea. Do financial transactions taxes really chill innovation? What are the consequences of zero welfare provision? How about if we legalise all drugs? Policies which would be impossible in a large democracy with a divided citizenry become possible in smaller communities of like-minded individuals.

So it is no surprise that seasteading is popular amongst libertarians like Thiel. And libertarian seasteads may indeed prove highly successful. But to see them as experiments in the ‘science’ of Politics is a rather dangerous mistake. Such ‘experiments’ have flawed validity; the citizenry of libertarian seasteads would end up a selective group blessed with talents and riches, who spend at least as much of their resources keeping the wrong people out, as letting the right people in.

Thiel criticises the US government immigration policy, as it prevents skilled foreign programmers from working in Silicon Valley. But the libertarian view of immigration has an ironic nuance. On the one hand, they often advocate open borders, arguing – admirably, if unrealistically – that no government should interfere with an individual’s freedom to roam the world as he wishes. On the other hand, in a libertarian society, where private property is absolute and everything is privatised, undesirable immigrants would have the same rights as trespassers, i.e. none. Some Seasteaders, fearful of climate change, have even begun building self-sustainable floating islands, impenetrable to climate refugees. Those foreign programmers on Silicon Island may be welcomed, but only at their host’s discretion. The poor, the destitute, the dispossessed, and the sick need not apply. The taxpayers on the mainland who funded the Seasteaders’ education can also forget about getting anything back.

Libertarian seasteads will be the preserve of the rich, and cut free from the draining demands of the rest of society they may well thrive. But this would hardly be a lesson for the rest of us. Those of us who know that the earth is not an infinite plane, also know that the challenge of building a good society means caring for all. The success of selective libertarian islands would constitute the failure of humanity to work together for an equitable future in a prosperous world.