So there's that change of general consciousness, and then there's this boom after the war, this expansion into the West. It was like the 1950s. The American economy was pumping at top speed. The kinds of people who would move into these communities and organize their lives around a utopian dream now had dreams about the West.

The Enlightenment faith that things are getting a little bit better each decade becomes difficult to support. People recognized that there had just been a war that was worse than the war of 1812, and worse than the Revolution; things were clearly not getting better and better.

But if you'd only ever lived in small wooden house in the middle of wilderness, it sounded much better. Especially because it provided intense community, and these people lived in incredible isolation.

Utopian fiction is really boring. I had to read a lot of it, and it's not that much fun. But they're fascinating to me as historical documents. Cabet [Icaria's founder and author of the utopian novel, Travels in Icaria], is writing in the 1830s, and his idea of the perfect society reveals a lot about his time. But his book is uniquely bad.

The thought was, 'We're going to go to California, where the soil is black and ten feet deep, and there are no rocks, and there's gold in the hills.' The West becomes the surface onto which people project their fantasies, where once the future had been the place they projected their fantasies. So it's not just the war that ends the utopian communities, but what follows.

Some people just think utopians are idiots who are imagining rivers of candy and not really engaging with the world's ills, and sometimes that's surely the case, but I think that imagining the perfected society is a way of expressing your disgust with the current state of affairs.

That to me was one of the most exciting, and weird puzzles of this book: how are the most religious people and the least religious people of their time all drawn to very similar visions of utopia?