I was recently thinking about writing in terms of articulation. The word "articulation" has as its root the Latin word "articulus", or "small connecting part."
It's easy, when writing, to let the flow of ideas carry us from one point to the next, without clearly indicating the articulation: the ideas that we flow through--one to the next--are not uniform--they are, in our heads, articulated, but in writing they are not if the flow of the writing does not make an effort to show where he one idea moves to the next. In this sense we want to "articulate" our writing in the sense that "articulation" is "the formation of clear and distinct sounds in speech": we want each idea to sound clearly and distinctly.
How can we accomplish this in writing?
One good way to do this is to break the work into sections, and to break the sections into subsections.
Our writing, of course, is broken into the small sections of words, sentences, and paragraphs, and we also break it into chapters, for very large works. But we can create divisions at a scale in between these extremes: we can group paragraphs into little sub-sections related to specific ideas, and these groupings of paragraphs can also be grouped into larger subsections that help divide the chapter into pieces.
By articulating the written work, we can help the readers in their effort to read, but we can also help ourselves organize the work: by breaking the larger work into smaller pieces, we can manage the effort of the project more efficiently, but by including explicit descriptions of how each little piece connects to the larger project and to the other pieces around it, we can can work on one piece at a time, secure in the knowledge that the piece will fit with the others--because it was written in relation to the others, and attempts to connect to them.