Puzzles and sports, crosswords to cricket, sudoku to soccer, are all pseudo-problems, artificial obstacles that bear a resemblance to natural problems, the flooded river and the broken car, but have certain properties so different that they should be distinguished and considered separately. For one thing, puzzles and sports are accepted voluntarily, natural problems are avoided if at all possible, though in prosperous times bored individuals invoke natural features, deserts, wild seas, and mountains, as artificial problems, "because they are there". A puzzle or a sport, of course, is undertaken for the pleasure and the delight of the solution, not because the need for the solution is necessarily forced upon you by threatening circumstance.

What further, and more interestingly, distinguishes these pseudo-problems from natural problems is that they are tractable, and they are tractable because they are designed to be solved, which the world's spontaneous difficulties are plainly not. Every aspect of a man-made puzzle invites solution, whereas natural problems are chaotic, a mighty maze indeed, but all without a plan.

Most importantly, puzzles invite solution through a rich structure, which like a novel contains little redundancy; indeed, there is a case for thinking that puzzles stand in relation to the crises of day to day life much as fiction stands to the chronic narrative of our lives. In between these two categories lies detective fiction, combining the most addictive elements of both, and confirming this literary continuum. How odd, therefore, that we know vastly more than we need to about the great fiction writers of the last two centuries, and almost nothing about the great concocters of conundra that, all told, most probably have more readers and have occupied more human time than any other cultural artefact. When next on a train, just look around you.