One of the major problems encountered in time travel is not that of becoming your own father or mother. There is no problem in becoming your own father or mother that a broad-minded and well-adjusted family can't cope with. There is no problem with changing the course of history—the course of history does not change because it all fits together like a jigsaw. All the important changes have happened before the things they were supposed to change and it all sorts itself out in the end.The major problem is simply one of grammar, and the main work to consult in this matter is Dr. Dan Streetmentioner's Time Traveler's Handbook of 1001 Tense Formations. It will tell you, for instance, how to describe something that was about to happen to you in the past before you avoided it by time-jumping forward two days in order to avoid it. The event will be descibed differently according to whether you are talking about it from the standpoint of your own natural time, from a time in the further future, or a time in the further past and is futher complicated by the possibility of conducting conversations while you are actually traveling from one time to another with the intention of becoming your own mother or father.Most readers get as far as the Future Semiconditionally Modified Subinverted Plagal Past Subjunctive Intentional before giving up; and in fact in later aditions of the book all pages beyond this point have been left blank to save on printing costs.The Hitchhiker's Guide to the Galaxy skips lightly over this tangle of academic abstraction, pausing only to note that the term "Future Perfect" has been abandoned since it was discovered not to be.
It comes from a very ancient democracy, you see...""You mean, it comes from a world of lizards?""No," said Ford, who by this time was a little more rational and coherent than he had been, having finally had the coffee forced down him, "nothing so simple. Nothing anything like so straightforward. On its world, the people are people. The leaders are lizards. The people hate the lizards and the lizards rule the people.""Odd," said Arthur, "I thought you said it was a democracy.""I did," said Ford. "It is.""So," said Arthur, hoping he wasn't sounding ridiculously obtuse, "why don't people get rid of the lizards?""It honestly doesn't occur to them," said Ford. "They've all got the vote, so they all pretty much assume that the government they've voted in more or less approximates to the government they want.""You mean they actually vote for the lizards?""Oh yes," said Ford with a shrug, "of course.""But," said Arthur, going for the big one again, "why?""Because if they didn't vote for a lizard," said Ford, "the wrong lizard might get in. Got any gin?""What?""I said," said Ford, with an increasing air of urgency creeping into his voice, "have you got any gin?""I'll look. Tell me about the lizards."Ford shrugged again."Some people say that the lizards are the best thing that ever happenned to them," he said. "They're completely wrong of course, completely and utterly wrong, but someone's got to say it.""But that's terrible," said Arthur."Listen, bud," said Ford, "if I had one Altairian dollar for every time I heard one bit of the Universe look at another bit of the Universe and say 'That's terrible' I wouldn't be sitting here like a lemon looking for a gin.