How much can the supporting sentences deviate from the topic sentence before introducing a second paragraph becomes a better option?

Question

My question is: How much can one deviate from the topic sentence before transitioning to a second paragraph becomes a better idea?

For example, if a topic sentence consists of an assertion, then the reader will assume that the supporting sentences list reasons that would convince them of that assertion. The paragraph will be coherent if I then proceed to list positive reasons for why the assertion is true, but I was wondering if it is possible to insert something like a comment to emphasize the strength of one of the reasons of a supporting sentence, such as "after all, if this were not true it would be...".

Such a comment somewhat deviates from the topic while still ultimately supporting it since it provides a negative reason for the contrary rather than a positive reason for the assertion. In that case, would a negative reason disrupt the flow of the paragraph, and would it be a better idea to transition to a separate paragraph in which the focus is on negative reasons for why the assertion of the previous paragraph should be accepted as true?

Perhaps I'm using a bad example, but this is the best I could come up with.

Answer 1

The paragraph is a very ill-defined unit of composition, and the rules of paragraph writing that they teach in schools (which is a kind of mini-essay format) has not a lot to do with how actual working writers write today.

For certain, the paragraph has been getting shorter. In the 19^th century you might have one or two paragraphs on a page and a single paragraph might contain an entire argument, with thesis statement, arguments pro and con, and conclusion.

Today that same passage would likely be broken up over four or five paragraphs.

By the same token, writers today are much more likely to break up a long chapter with subheadings, something you would rarely if ever see in a 19th century work.

So it is perhaps easier to think of things this way: A piece of writing needs to be broken up with breaks or pauses of various sizes to indicate to the reader some change of subject or direction. The break between sentences is the smallest of such breaks. The break between paragraphs is the next largest. The break between sections next, then chapters.

The 19^th century style essentially worked with three breaks: sentence, paragraph, and chapter. We now work with four: sentence, paragraph, section, and chapter. The paragraph break is thus a more minor break today than it was in the 19^th century.

Ask yourself, therefore, if you think the reader will need a slightly larger break than a break between sentences, and, if so, create a paragraph.

Some may complain that you have too many paragraphs or too few, but this is not exact science. Do what seems to make for a comfortable read and you won't go too far wrong.

Answer 2

There are two ways to think of the paragraph:

1. as representing the structure of the content of your text, and
2. as visually structuring your text to help orient the reader.

On the internet, visual structure is essential. Paragraphs on websites such as this one have a line of whitespace between them, and paragraphs are shorter. Both help the reader not to lose where they were, given lines that are usually too long (60 characters are ideal), text that is too small (18 px is ideal), and the many distracting links, menues, advertising, and other content that draws their attention away from what they are reading.

In a book, on the other hand, the layout is usually almost ideal, there are no distractors (at least not on the page), and the page does not scroll and orientation is much easier. Therefore, paragraphs may be longer without confusing the reader and more closely reflect the internal structure of the text.

If you disregard visual structure to help the reader and look at the internal structure alone, then a paragraph is best thought of as something that feels unified to you, and a paragraph break happens when you feel that something you wanted to say has been wrapped up and you want to start in on something else.

Whether you make a paragraph break only when you have completed an argument, or also whenever you deviate to a "side argument", is a matter of personal style. We are not in school, and you may write however you feel best reflects your way of thinking. That other writers would break up the same text in another way, is irrelevant. The only thing that counts is that your structure feels right to you.