The First Galactic Empire had endured for tens of thousands of years. It had included all the planets of the Galaxy in a centralized rule, sometimes tyrannical, sometimes benevolent, always orderly. Human beings had forgotten that any other form of existence could be. All except Hari Seldon. Hari Seldon was the last great scientist of the First Empire. It was he who brought the science of psycho-history to its full development. Psycho-history was the quintessence of sociology, it was the science of human behavior reduced to mathematical equations. The individual human being is unpredictable, but the reactions of human mobs, Seldon found, could be treated statistically. The larger the mob, the greater the accuracy that could be achieved. And the size of the human masses that Seldon worked with was no less than the population of the Galaxy which in his time was numbered in the quintillions. It was Seldon, then, who foresaw, against all common sense and popular belief, that the brilliant Empire which seemed so strong was in a state of irremediable decay and decline. He foresaw (or he solved his equations and interpreted its symbols, which amounts to the same thing) that left to itself, the Galaxy would pass through a thirty thousand year period of misery and anarchy before a unified government would rise once more. He set about to remedy the situation, to bring