A Guide to Writing in History
(based on A Guide to Writing in History and Classics by M. Damen)
A paragraph is one of the greatest tools you have in organizing your writing. It's a simple, almost subconscious way of cluing your reader in on the divisions that underlie your thinking. Ideally, a paragraph delineates a thought. In antiquity, a paragraph often was a single thought—and often a single sentence, usually a very long one. Writers today, however, tend not to go on the way classical authors did. In academic writing, most paragraphs include at least three sentences, though rarely more than ten.
So, how many paragraphs are enough, and how many are too many? For historical writing, there should be between four and six paragraphs in a two-page paper, or six and twelve in a five-page essay.* More than that, and it becomes difficult to see the larger contours of your argument. Fewer, and it's hard to see where sections start and end. A good general rule is two to three paragraphs a page.
But there's considerable flexibility here, too. So, perhaps it's better to look at paragraphs another way, from the inside. Instead of surveying the paper as a whole, you can count sentences within paragraphs. If so, all paragraphs should have between three and ten full sentences. All in all, a strong and coherent paragraph starts and ends itself, and so there's no need to count paragraphs when the argument is clear and directed.
In sum, remember the point of paragraphs is to show the structure of your thoughts. A paragraph should encompass one thought—that is, it should have some idea guiding it—which is then divided into separate sentences all of which address and advance that idea. So, insert a paragraph break when you are making a transition between ideas, or adding a new line of thought, or when you've finished summing up, as I'll do right now.
*You should be aware these standards will vary from class to class, even within historical disciplines. So, for instance, journalists tend to write in many short paragraphs. The same is true in some of the sciences. Just know that many short paragraphs are generally to be avoided here.