Einstein began with the equivalence principle. Once that premise was taken seriously, an entirely new picture of gravity began to unfold, and general relativity naturally followed. Now we have a similar premise: humanity will soon hit the limits of our home planet. Becoming multiplanetary is not merely an option; it is our inevitable destiny. Once that is truly understood, much of what Elon and SpaceX are doing stops looking extreme or disconnected. Starship, rapid reusability, Starmind, enormous launch capacity, lunar outpost, Mars settlement, all of it follows naturally from the same underlying logic.