After the Great Revolt against the Thinking Machines, the Butlerian Proscriptions banned all forms of advanced computational technology and artificial intelligence. All spacecraft, dependent on AI for propulsion or to navigate through folded space, were abandoned, plunging entire planetary systems into dangerous isolation. The inevitable collapse of intergalactic commerce and communication plunged humanity into a new dark age.
Then, in 88 BG, Tio Holzman's assistant, Norma Cenva, discovered that the mind-altering properties of the spice-drug mélange induced a form of enhanced awareness and limited prescience. This ability allowed Cenva to perform the delicate calculations necessary for successful foldspace navigation without sophisticated technology.
Norma Cenva’s discovery allowed the resumption of intergalactic travel and led to the eventual establishment of the independent Spacing Guild, with her as the first Navigator.