Ted Chiang’s “The Merchant and The Alchemist’s Gate”, “What’s Expected of Us”, and “Story of Your Life” beautifully demonstrate that both time travel and infallibly predicting the future are possible. But, if, like me, you’d love to have a time machine or a Predictor, don’t get your hopes up. With just a little philosophy, we can see that these technologies, though possible, are unlikely to ever exist. No engineering or physics required.