In some of the best versions of reality, the Egyptians discover America, the industrial revolution happens early, and eventually robots take over. In others, the Renaissance produces a plutocracy, which leads to a utopia. Or perhaps to anarchy; it's all in thesubtle details. As a time traveler, you've seen it all, and it all has its place. What's important is who's in control in the long run, when time travel is invented. With other time travelers mucking with things for their own reasons, your course is clear: you wiltamper with history as much as is needed, step on however many butterflies it takes, to get a perfect world, under your own benign rule.