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 about a state of affairs that would restore peace and civilization in a single thousand of years. Carefully, he set up two colonies of scientists that he called "Foundations." With deliberate intention, he set them up "at opposite ends of the Galaxy." One Foundation was set up in the full daylight of publicity. The existence of the other, the Second Foundation, was drowned in silence.
In Foundation (Gnome, 1951) and Foundation and Empire (Gnome, 1952) are told the first three centuries of the history of the First Foundation. It began as a small community of Encyclopedists lost in the emptiness of the outer periphery of the Galaxy. Periodically, it faced a crisis in which the variables of human intercourse, of the social and economic currents of the time constricted about it. Its freedom to move lay along only one certain line and when it moved in that direction, a new horizon of development opened before it. All had been planned by Hari Seldon, long dead now.
The First Foundation, with its superior science, took over the barbarized planets that surrounded it. It faced the anarchic Warlords that broke away from the dying Empire and beat them. It faced the remnant of the Empire itself under its last strong Emperor and its last strong General and beat it.
Then it faced something which Hari Seldon could not foresee, the overwhelming power of a single human being, a Mutant. The creature known as the Mule was born with the ability to mold men's emotions and to shape their minds. His bitterest opponents were made into his devoted servants. Armies could not, would not fight him. Before him, the First Foundation fell and Seldon's schemes lay partly in ruins.
There was left the mysterious Second Foundation, the goal of all searches. The Mule must find it to make his conquest of the Galaxy complete. The faithful of what was left of the First Foundation must find it for quite another reason. But where was it? That no one knew.
This, then, is the story of the search for the Second Foundation!