In his book A Dash of Style (2006), a "practical and accessible guide to the art of punctuation for creative writers," Noah Lukeman discusses an important yet frequently overlooked mark of punctuation--the paragraph break.
Few people would think of the paragraph break as a punctuation mark, but it certainly is. In ancient times there were no paragraphs--sentences simply flowed into one another without interruption--but over time text became segmented into paragraphs, at first indicated by the capital letter "C." During medieval times this mark evolved into the paragraph symbol [ ΒΆ] (called a pilcrow or a paraph) and this eventually evolved into the modern day paragraph break, which is, of course, indicated today by only a line break and indentation. The indentation we use today was originally there for early printers, so that they would have space for the large illuminated letter which used to herald paragraphs. The illuminated letter no longer exists, but, luckily for tired readers, the spacing does.
Today the paragraph break is indicated only by absence, which is perhaps why it is glossed over in discussions about punctuation. This is a shame, because it is one of the most crucial marks in the punctuation world. It is used thousands of times in any given book, and on its own it can make or break a work. Few places are more visible than the beginnings and endings of paragraphs: with their ample spacing, they are eye-catching. As such the paragraph break has an unparalleled ability to propel into the limelight, offering perpetual opportunities to grab readers with new hooks. It has the unique power to frame a cluster of sentences, to give them shape and meaning, to resolve the theme of the current paragraph and set the stage for the paragraph to come. Indeed, this is why some speed-reading courses teach readers to read merely the beginnings and endings of paragraphs.
The paragraph break is a big brother to the period: the period divides sentences, while the paragraph break divides groups of sentences. Just as a sentence must have a beginning and appropriate ending, so must a paragraph. Yet while the period is paid homage to as the backbone of punctuation, the paragraph break is largely ignored. This is ironic, since its role could be considered even more pivotal than the period, as it affects not just one sentence, but many. If the period is a stop sign, then the paragraph break is a stoplight.
(Noah Lukeman, A Dash of Style: The Art and Mastery of Punctuation. W.W. Norton, 2006)
Paragraph breaks tend to occur more frequently in some forms of writing (emails, blogs, and newspaper articles, for instance) than in others (such as essays and research papers). But in prose of all kinds, paragraphs (like the sentences they contain) tend to be shorter today than they were just a century ago. So as you revise your own writing, consider giving your longer paragraphs (and your readers) an added break.
To learn more about paragraph breaks and paragraphing, see the following articles and exercises: