That's the job of the magical Traveller, to use his magic to end magic. That underlying paradox provides the premise of this connected set of short stories. He travels the world at intervals, surveying the realm of unreason on each trip, and taking satisfaction in watching it shrink. Where he can, he applies his subtle magic in support of Reason's expanding domain.
Brunner explores Chaos's control and degradation of humankind in several of its ways. The first story tweaks mindless religion. It might even show how one can choose atheism, after encountering a god face to face and finding him unworthy of belief. Another of these gentle stories undermines magical thinking - again, not because it fails, but because its success is not worth having. And so with the faith in luck that makes Las Vegas the holy city of Chance, and so the unwarranted sense of entitlement that demands ever-richer result for ever-poorer effort at earning it, and so for blind pursuit of power irrespective of the cost or of who pays it. Since these stories are built around layers of paradox, Brunner's mechanism is itself a paradox, the smallest of magics to achieve the largest of consequences.
Brunner was one of the best SF writers of the 70s and 80s, author of "Shockwave Rider" and other stories of chilling prescience. Among all of his writings, though, "Traveller in Black" may be his finest and most under-stated, under-rated achievements. These stories have held up well over the thirty years since they were written; since they pass in a distant place and age, there is little in them that can look dated. I recommend these stories to any thinking reader.