Automata theory, body of physical and logical principles underlying the operation of any electromechanical device (an automaton) that converts information from one form into another according to a definite procedure.
About 20 years before the story takes place, solar flares irradiate the Earth, killing over 99% of the world's population. The survivors gather in a network of safe cities and build primitive humanoid robots, called Pilgrims, to help rebuild and operate in the harsh environment.