I had an interesting discussion with an author this week who wanted to know if she should change her sections -- with headings -- into chapters. Her book is presently divided into five chapters representing five decades, with sections within each chapter clearly delineating the action. It works.
When she asked if sections should be changed into chapters, I had to think a bit before saying that it really didn't matter. Call a division what you will -- a section or a chapter -- and it's the same thing. A chapter isn't a real unit. It's just an agreed-upon segment, something to help the reader make sense of a very long work of prose, and it doesn't actually have to exist. The only reason it does exist is because people seem to want it.
I looked up "Chapter" in the OED, and was charmed to find this:
A later syncopated form of CHAPITER, a. OF. chapitre, earlier chapitle: L. capitulum. dim. of caput head, used, in ancient Latin, in the senses ‘little head, head of a plant, capital of a column’, and later, those of ‘head-dress of women, chapter of a book, section of a law’. The form chapter appears in Sc. in 14th c., but in Eng. is rare before the 16th; chapiter survived beside it till the middle of the 17th, and is still occasional in the sense ‘capital of a column’. Cf. also CAPITULUM, CAPITLE, CHAPITLE, CHAPITER, all orig. the same word. 1. a. A main division or section of a book (whether the latter is an entire literary work, or one of the divisions or parts of a large work). Esp. used of the main divisions of the books of the Bible. Cf. BOOK n. 8.
I'm not surprised that it was first used in reference to the Bible, since for a long time that was probably the longest book of which anyone knew, and the one that most easily lent itself to chapters. But within those chapters were something else entirely -- verses! And we rarely see a book today divided into chapters and verses, do we?
Perhaps we should.
By the way, did you know "chapter" can also be a verb? "I chaptered my book." It hasn't been much in use since the 1800s, but I rather think it's due for a comeback.