Bridle and Saddle
The Mayors, occurs three decades after The Encyclopedists, The Foundation's scientific understanding has given it unusual leverage over nearby planetary systems, and its control is exercised through an artificial religion referred to as Scientism. This concept allows the Foundation to share the benefits of its advanced technology, while keeping its scientific secrets. Maintenance technicians known as priests are trained on Terminus and given basic operational understanding of the technology, while being kept ignorant of the underlying scientific knowledge. Thus, the Foundation is able to quell the anti-scientific rebellions and delocalisation of knowledge which have reduced the rest of the galactic periphery to barbarism.
Mayor Salvor Hardin, as Mayor of Terminus, is the effective ruler of the Foundation. Prince Regent Wienis of Anacreon plans to overthrow the Foundation's power, and his plans are encouraged when he obtains an abandoned Imperial cruiser that he demands the Foundation repair.
Hardin foresees Wienis's plans and arranges for the ship to be repaired his own way, incorporating some modifications. Hardin then broadcasts Wienis's attempt to the people of Anacreon under the ruse of blasphemy, leading to a revolt which results in direct control over the Four Kingdoms.
Hari Seldon again confirms the actions by appearing in the "Time Vault", while also warning them that Scientism, while adequate to defend the Foundation from the immediate threat, will not be sufficient to expand its influence beyond its barbarous near-neighbors.