Those seeking in philosophy a guide for the perplexed should be warned. While philosophy can enlighten, it can also mislead and delude. As Descartes observed, 'The greatest souls are capable of the greatest vices as well as the greatest virtues.' This book explores the perils of philosophy. It shows that philosophers' own behaviour, sometimes bad, sometimes sad, occasionally downright mad, is seldom entirely unconnected with their thinking. Philosophers Behaving Badly examines the lives of eight great philosophers: Rousseau, whose views on education and the social order seem curiously at odds with his own outrageous life; Schopenhauer and Nietzsche, two giants of the nineteenth century whose words seem ever more relevant today; and five immensely influential philosophers of the twentieth century: Russell, Wittgenstein, Heidegger, Sartre and Foucault. All of which will show that the life of reason does not necessarily lead to a reasonable life.