Back in December of 2012, Zed Shaw wrote an essay entitled Indirection Is Not Abstraction (if link is broken). In this, Shaw notes that there are a few misconceptions about the definitions of several terms used to describe methods of modular design and code isolation: interfaces, abstractions, and indirection. Basically, he suggests that our fellow coders and engineers mix them up and conflate them with other concepts.
The article is clearly a bit of a work in progress, as noted by Shaw himself in the concluding paragraph. It is not particularly well-written or well-structured. Shaw uses a writing style that conjures this image of the ever irritating shock-jock. If there is something he doesn't like, he emphasizes with expletives. If there is someone he doesn't like, he will go out of his way to find the room to take a shot at them. For instance, later on, Zed Shaw manages to inexplicably slip in a link to a search for "Dave Winer Asshole."