Book excerpt: Does humour make us human, or do the cats and dogs laugh along with us? On Humour is a fascinating, beautifully written and funny book on what humour can tell us about being human. Simon Critchley skilfully probes some of the most perennial but least understood aspects of humour, such as our tendency to laugh at animals and our bodies, why we mock death with comedy and why we think it's funny when people act like machines. He also looks at the darker side of humour, as rife in sexism and racism and argues that it is important for reminding us of people we would rather not be.