As Alain de Botton's best-seller and TV series on Channel 4,The Consolations of Philosophy, have shown, philosophers can stimulate thought hundreds, even thousands, of years after their death. De Botton has concentrated on the idea that philosophy can be a form of self-help. If you suffer from anger, learn from Seneca that it's a useless emotion, and pick up tips on how to control it; if you're unhappy in love, learn from Schopenhauer that sexual attraction is all about biology and not about fulfillment.
This image of philosophy as psychotherapy is not a new one: it dominated Roman philosophy. But it's not the only way that dead philosophers can speak to us today. One of …