From the text:
WELCOME TO THE MACHINE
It is the future, but how long it has been since humanity fell no one knows. The world is different now, for all minds exist only within the Machine, the great being known as KEETON. Mankind only exists in its vast computer substrate, and free-thought is only available to those who would fight. The world is a perfect recreation of how it was when the Machine was switched on, in the early part of the current century. KEETON refuses the idea of free-thought and uses concrete belief to track those rebels who would fight against him to try and get back to the physical world.
The only rule in Alpha Gamma is this: if a character (and player) can avoid stating anything absolutely, then they can succeed. If they, at any point, reify any ideas, then the Machine imposes penalties on them.