The science of historical prediction and macrosocial manipulation.
The main thesis of psychohistory is that the action of trillions of individuals take on a fluidity and predictability which can be compared to that of molecules in a gas. The very size of the population being dealt with factors out individual peculiarities and allows the prediction of its behavior. With the ability to predict the reaction of a population to a particular stimulus comes the ability to memetically manipulate that population, for example through a combination of public relations/advertising techniques and behavioural science. As far back as the middle Consolidation period, simulation experiments by independent institutes, including the Cislunar Wilber Institute, the Perl School of Sub-Singularity Psychology, Corona, and the Institute of Long-Range Cliology, Eklund ISO, have decisively confirmed the validity of the science, but the number of disruptive variables in any community open to its environment were shown to increase exponentially as a value of time, rendering long-range real world prediction impractical even given a nebula-brain processing capacity.