The Nexx Timecasters saw clearly that that tampering of prior eras were all part of a grand pattern of confusion; that any effort to manipulate reality via temporal policing was doomed only to further weaken the fabric.
When you patch time, you poke holes in it; and patching the patches makes more holes, requiring still larger patches. It’s a geometric progression that soon gets out of hand; each successive salvage job sends out waves of entropic dislocation that mingle with, reinforce, and complicate the earlier waves—and no amount of paddling the surface of a roiled pond is going to restore it to a mirror surface.
We can be sure that time travel doesn’t exist because if it did some paradox would surely have already ripped apart the fabric of space-time and destroyed the universe. Mankind can’t even master the art of flushing the toilet in a public restroom; there is little hope that he could learn how to safely manipulate the ylem. A similar idea is presented in a much more thoughtful way in Keith Laumer’s Dinosaur Beach: Arthur can pull the sword from the stone and Christ can open the seventh seal, but in the novel, there does not appear to be a champion worthy to be a Lord of Time. The strongest candidate is Nexx Central, an organization of timesweepers who are attempting to stabilize the temporal structures damaged by the Third Era timesweepers, who were trying to undo the mess from the Second Era timesweepers, who were trying to clear out all the chronic debris from the First Era temporal experimenters, and so on, and so on…
Nexx has established a base of operations on a beach in the middle of the Cretaceous, which is promptly blown up in the opening pages by machines from the Third Era. The story concerns timecaster agent Ravell as he finds himself stranded in multiple timelines and forced to battle against a machine supergenius for control of the great stem of time.
Laumer delights in his many twists, paradoxes, timelines, and mind-bending reversals, and this reader did too. Highly recommended.