I love the story recounted in this marvellous book by Richard Dawkins about the meeting of two old friends, both Cambridge mathematicians. The Indian, largely self-taught genius Ramanujan was in hospital, on his deathbed, in Putney in 1920. His colleague G.H. Hardy called. ‘Hardy, always inept about introducing a conversation, said, probably without a greeting, and certainly as his first remark: “I thought the number of my taxicab was 1729. It seemed to me rather a dull number.” To which Ramanujan replied: “No, Hardy! No, Hardy! It is a very interesting number. It is the smallest number expressible as the sum of two cubes in two different ways.”‘ It takes a trained, alert mind to see a thing for what it has the potential to be.