At a party, two years ago, Tony Hoare and I were approached by a mathematician who expressed his delight in meeting two such outstanding computing scientists for he had never been able to understand what he had to do in order to save a file on his personal computer, model so-and-so. We could not help him and Tony asked him, whether he could recommend a book on category theory; he could not help Tony either.

An anecdote by Dijkstra