(Dr. Seldon is on trial):
Q. You quibble, Dr. Seldon. Can the overall history of the human race be changed?
A. No. With great difficulty.
A. The psychohistoric trend of a planet-full of people contains a huge intertia. To be changed it must be met with something possessing a similar inertia. Either as many people must be concerned, or if the number of people be relatively small, enormous time for change must be allowed. Do you understand?