The Russian-American novelist Ayn Rand believed that behaving rationally meant putting your own interests first: you actually have a moral duty to be selfish. Altruism or self-sacrifice are immoral, she claimed, as is asking for help from others. Clearly this goes against most traditional views of ethics, but Rand's views have become influential, particularly in some corners of American politics.

Rand's protege, Nathaniel Branden, developed her ideas to stress the importance of self-esteem - the route to personal fulfilment was feeling good about yourself. Many people, even those who would reject Ayn Rand's core philosophy, have subsequently believed that low self-esteem is at the root of social problems such as crime and educational underachievement, and that we should aim to boost it.

But is self-esteem really such a good thing? As Paul Broks discovers, the research suggests that some people have too much self-esteem, not too little. Maybe the route to a good life is not through feeling good about yourself, but being resilient to knocks that fate deals you.