The trilogy revolves around the concept of psychohistory, a science that enables people to accurately predict the future. Its originator, psychologist Hari Seldon, uses psychohistory to predict the fall of the Galactic Empire and then establishes the Foundation (a planet of physical scientists) and the Second Foundation (a group of psychologists).

The purpose of the Foundations is to truncate the amount of time that humankind will spend in the dark age that will inevitably follow the fall of the Galactic Empire.

The ability to predict the future through psychohistory is the key to the Foundation's success against its barbaric neighbors, but the ability is found less in scientific specialists than in common-sense, empirical thinkers such as traders and politicians. Psychohistory predicts only the actions of masses of people and deals only in probabilities, so that individual choice still exists. Nor can psychohistory predict the...