Some philosophers - the gloomy German, Schopenhauer, was one - have made a whole philosophy out of pessimism. I doubt that Schopenhauer was a bundle of laughs or that a good dose of hormones would have turned him into a giggling optimist. Indeed, the most common view was that serious people, such as sages and philosophers, were not bubbly and smiley, because they saw life as more or less tragic. A man who met the great 18th century sage, Samuel Johnson, in London, listening to his talk, said: "Dr Johnson, you are a philosopher. I, too, tried to be a philosopher in my youth, but cheerfulness would keep breaking through."