[...] This ‘Grandfather Paradox’ seems to tell against time travel’s possibility.Within philosophy the most famous contribution to this debate is David Lewis’s ‘The Paradoxes of Time Travel’. We could travel in time, says Lewis, but don’t think you can thereby do the impossible – that (unsurprisingly!) is something you will definitely fail to do. If you go back in time and try and bring about a paradox, then something will get in your way. Perhaps you slip on a banana peel and miss, perhaps the gun jams, perhaps you bump into the man/woman of your dreams and decide an evening of romance is better than an evening of blood-soaked ancestor murder, perhaps… well, lots of things might stop you. Lewis nonetheless assures us that one of those possibilities will definitely come about if you go back in time and try.