Dionisio explicó, amargamente, que su vida estaba siempre pendiente de amenazas, y que si Damocles quería ser tirano durante una noche, debía soporta… - Isaac Asimov

It seems perfectly obvious that, since Terminus cannot defend itself, Anacreon must take over the job for its own sake. You understand we have no desire to interfere with internal administration — ' 'Uh-huh,' grunted Hardin dryly. ' — but we believe that it would be best for all concerned to have Anacreon establish a military base upon the planet.

Chen said, "Dr. Seldon, you disturb the peace of the Emperor's realm. None of the quadrillions living now among all the stars of the Galaxy will be living a century from now. Why, then, should we concern ourselves with events of three centuries distance?"

First Law of Robotics. You know that it is impossible for a robot to harm a human being; that long before enough can go wrong to alter that First Law, a robot would be completely inoperable. It's a mathematical impossibility.