Is it permissible to use subconclusions for argumentative paragraphs if they contain multiple arguments in support of the main point?

Question

Argumentative paragraphs often contain a topic sentence that states the main point, and the main point tends to be supported by multiple arguments that are introduced throughout the paragraph as First, Second, and Last. My question is whether I, in the case of a long paragraph, can use subconclusions (such as a sentences beginning with Thus, So, or Therefore etc.) for the First and or Second arguments, or whether I always have to wait and summarize all points in a final concluding sentence? The paragraph would be structured as follows:

Beginning of the paragraph
Topic sentence
Argument 1
So, this is why argument 1 ...
Argument 2
Thus, argument 2 implies ...
Argument 3
Concluding sentence
End of the paragraph.

Answer 1

It is certainly permissible because outside of specific educational programs, there are no prohibitions on paragraph structure that would make it impermissible. That topic-sentence etc. model is simply a particular systems of training wheels and there are innumerable good paragraphs that don't fit the model. Indeed, writing would be tedious if they did. In particular, summarizing points in a concluding sentence is laborious and unnecessary most of the time. Paragraphing today has more to do with the ergonomics of reading (breaking up long paragraphs for readability) than the structure of argument. And, finally, note that this paragraph is an example of the kind of paragraph you are describing.

Answer 2

My question is whether I, in the case of a long paragraph, can use subconclusions (such as a sentences beginning with Thus, So, or Therefore etc.) for the First and or Second arguments, or whether I always have to wait and summarize all points in a final concluding sentence?

Neither. You should try to avoid beginning sentences with those words altogether.

Rhetorical writing is not a series of three-line syllogisms. Your audience is smart enough to understand how juxtaposed sentences relate to one another. There is no need for this sort of "noise word" at the beginning of a conclusive sentence. They are occasionally useful to emphasize a more subtle logical implication. But if you find yourself raking your mind for more synonyms of these words, you are probably using them too frequently. Similarly, paragraphs need not obey any fixed format. Their purpose is to aid the reader by grouping together related sentences and presenting them in a cohesive order. If a logical argument naturally flows into another, by all means combine them in a single paragraph.

On the other hand, a paragraph may consist of a single sentence.

Short paragraphs can serve a variety of purposes. They naturally draw the reader's attention, without the need for any obnoxious formatting such as bold or italic. This is particularly useful when the paragraph states a key point, or draws a deeper conclusion from multiple paragraphs before it. Short paragraphs also give the reader a little variety, and help to prevent "wall of text" fatigue. Like any attention-getting technique, they can be overused, but are very powerful when applied judiciously.