I’m in London to work on impossible.com, the social network I have been developing for two years. Impossible is a place where people can post things they want (from work experience to world peace), and things they’re prepared to give (from Mandarin lessons to website design). The idea is to use a social network to try to encourage a culture of giving and receiving. I’m doing it because I believe people are naturally generous, and that’s the kind of world I want to be in more often. I don’t know whether it’s a great or a ridiculous idea, but I have decided to invest in optimism. You just have to go off ‘faith, the fumes of faith, sometimes terrified’ to do something new, my friend Jony Ive says at a talk I go to — since all the data will tell you it’s not going to work.