Psychohistory is a new science developed by noted mathematician Hari Seldon. It has the ability to accurately predict future events.
Developed by noted mathematician Hari Seldon, Psychohistory is a combination of science and mathematics that uses probability and historical analysis to predict trends and patterns within large social groups. While it could not predict the actions of an individual, it could predict the behavior of large societal groups. With this new science, Hari Seldon predicted that the Galactic Empire would fall within five centuries, and be followed by a period of thirty thousand years of barbarism.
Housed within a device called the Prime Radiant is all of Hari's calculations regarding the fall of Empire. His theories caused concern within the Empire, and with the Emperors themselves who believed that Hari's predictions could cause faith in the Empire to be undermined. While recognising that the fall was inevitable, Hari knew that manipulating certain events could accelerate or slow the fall. In an effort to reduce the amount of years spent in a dark age, Hari proposed the creation of a Foundation to safeguard knowledge and civilization.
From the Foundation Books
Psychohistory is a form of science developed by Hari Seldon. Combining history, psychology, and mathematical statistics, the science can predict a nearly exact model of the behaviour of large groups of people. It is the study of the reaction of human conglomerates when exposes to to economic and social stimuli. Psychohistory was created by Seldon and expanded through the efforts of Dr. Gaal Dornick and other mathematicians.
Seldon used Psychohistory to predict the fall of the Galactic Empire and a following dark age lasting thirty thousand years. In an effort to stave off the barbarism that civilization would fall into, Seldon used his new science to nudge events in a certain direction that would see the dark age reduced to only a thousand years through the establishment of the Foundations, two groups of scientists and engineers tasked with the mission of preserving science and civilization.