This is a story that was published in a fantasy and/or science fiction magazine -- not sure if it ever appeared in any book collection. Sorry, I don't even know the name of the magazine, but it would have been an issue produced in or before 1989, likely some years before since the magazine was old when I read it in the late 80s.
Anyhow, the story: It's a surreal detective story where the main character (a Sam Spade type) tracks some mystery villain to his lair, where it is revealed that the villain has managed to isolate/refine the essence of the universe, which he calls The Nature of Things or some similar phrase.
If I recall correctly, this essence-thing is described as being like a tangle of fine wires, all interconnected, and it had to be handled with extreme care, as changes to it would change the universe. There is a scuffle, and it is dropped or dented, with the result that the main character's world becomes much darker and stranger.
The villain gets away, but the main character finds him again later (either on purpose or by accident). What I remember most clearly about the story is that, when the main character threatens to arrest the villain, the villain gestures to another net of strands in the trunk of his car and says something to the effect of: "Not now, man! Can't you see I've finally gotten down to The Basics?!"