When we draft, we tend to put the sentences down as they occur to us, which isn't always the best order to read them in.
There's a relevant discussion of structure in a famous dialogue by Plato called Phaedrus. Here is a paraphrase.
Soc. Lysias appears to have jumbled his sentences, begun at the end instead of the beginning. Don't you think, Phaedrus?
Phaedr. Yes, indeed, Socrates; he begins at the end.
Soc. There's no logical order to the sentences. He seems to have written them down as they occurred to him. Every discourse ought to be a living creature, having a body of its own and a head and feet; there should be a beginning, a middle, and an end, adapted to one another and to the whole?
Phaedr. Certainly.
Soc. Consider the following poem:
I am a maiden of bronze and lie on the tomb of Midas.Soc. In this rhyme whether a line comes first or comes last makes no difference.
So long as water flows and tall trees grow.
So long here on this spot by his sad tomb abiding.
I shall declare to passers-by that Midas sleeps below.
Phaedr. Indeed.
The point: If the order of a paragraph's sentences can be shuffled with no loss of meaning, the paragraph is unnecessarily hard to read.
I think Phaedrus should have disagreed. The order seems right to me. The speaker introduces herself, says who she is and what she is doing. The last two lines as originally printed should be separated by a coma instmead of a period because they form a single idea.
Meaning is created sentence by sentence. The first sentence in a paragraph should be self-evidently meaningful. Each subsequent sentence should modify that subject in a clear way. If you were to remove a sentence from a well-structured paragraph, it would seem to have a hole in it, like something important was missing. If you were to move the sentences around, the meaning would change because the structure changed.
Unless we think systematically before we start writing, creating outlines or topic lists, we will tend to write paragraphs sentence by sentence as each sentence occurs to us, which isn't always the best order to read the sentences in. We think associatively often with huge leaps that we don't notice because the assumptions those leaps are based on are
implicit
A psychologist at Stanford invented this simple game. Volunteers were given one of two roles:"tappers" or "listeners". Tappers received a list of twenty-five well-known songs, such as "Happy Birthday to You" and "The star-Spangled Banner." Each tapper was asked to pick a song and tap out the rhythm to a listener (by knocking on a table). The listener's job was to guess that song, based on the rhythm being tapped.
Try it. What are the chances of someone guessing what you are tapping?
Most people guess 50%. In practice, the success rate is roughly 2.5%
in our own thinking but absent from the words we write down. But once the sentences are down, they can look and sound right to the writer even when they won't to a reader. You need to read your own writing cold. Walk away for the rest of the day and pick it up in the morning. Alternatively, shuffling the sentences can make the structure or lack of structure more apparent to you. You can more readily see where a sentence should go, where a transitional word would help connect two ideas, and what sentences need their own paragraphs.
Well-formed informational paragraphs tend to have specific characteristics.
While signals are important, you need to use them judiciously. If a reader can see there are three paragraphs, do you need to write, firstly, secondly, in conclusion? Often we use signals to help us grasp the structure we are trying to create or identify. Once the structure is clear to us, these signals should be removed -- as I just said, that is to say, in a moment I will. Signals that help the writer don't necessarily help the reader.
If you are having trouble visualizing alternative orders, put each key idea (perhaps each topic sentence) on a PowerPoint slide and then use slide sorter view to sort and think,
An introduction should
A conclusion should
If you are creating a very long document, one that has more than say five lengthy sections, then you may want to link each big section to the next with a summary and forecast, a macro transition that helps your readers hold in working memory everything they need to fully understand the document. A typical summary/forecast looks something like: In this section we looked at A,B,C in order to R. In order to get from R to U, we will need to blah, blah, blah, which we will do in the next section. Be careful here, however. Meta discourse like this can help a reader, but often we will use it to help ourselves as we draft, to remind ourselves what this section is supposed to be about or to make a stab and making connections with subsequent sections. That kind of meta discourse is not helpful to readers and you want to make sure you eliminate it from the final version.
Select a paragraph from the drop down box. See if you can figure out what the original order is. If you want to challenge yourself, you can drag and drop the sentences to make them read the way you think the paragraph should. Then hit "go" to check your order against the original. If they match, the word "Awesome" appears on the screen. If not, a try again button will appear and you can go back and think some more. If you get frustrated, you can reveal the original by clicking "see original".
In a couple of cases, the original is no better than scramble. The author of those examples needed to revise the draft more than they did.
Because editing other people's writing is not the same as editing your own, after you have tinkered with some of the examples, tinker with some of your own. If you are struggling with a paragraph, copy it here and see if scrambling it tells you anything about how the sentences should relate to each other. Maybe one sentence will stick out as belonging to another paragraph (in which case delete that sentence and use it to start a new paragraph later). Maybe you will see more or less the same idea said twice (in which case combine and delete or just delete one.). If you don't know why each sentence follows its predecessor, something is wrong.