The second liberal delusion is to believe they have a truer grasp of people’s interests than voters themselves. In some cases that might be true. It is hard to see how abolishing health subsidies will help people who live in “flyover” America. But here is the crux. It does not matter how many times Mr Zuckerberg invokes the magic of online communities. They cannot substitute for the real ones that have gone missing. Bowling online together is no cure for bowling offline alone.