My father used to tell me that, when trying to make a point, tell them what you are going to say, then say it and then tell them what you've said. Growing up, I tried to follow this advice, but found that my elders and later my peers, rarely had enough patience to tolerate such a wordy, formal approach. In time, I learned to assess their attention spans and to conform the structure of my arguments to those limits. In the process, I found that such a fluid approach is more successful than Dad's classic rhetorical style.
As an author, it is good that you know the point that you are trying to make and it is even better that you have divided that point into a series of progressive assertions which build a case for your conclusion. But none of that frees you from your other obligations as a writer. You must engage your readers and make their passage through your creation energetic, lively, and drudgery free. By using foreshadowing and deferred explanation, you should make them hungry for future pages while keeping each current page fast paced, concise and definitive.
One sentence which delivers your assertion in minimal words yet with perfect clarity, is infinitely superior to three or more, less artistically-crafted sentences, following the classic argumentative style. With modern attention spans, even that perfect sentence might be better delivered as a bullet point.
We are living in an age when the guardians of publication have been dethroned and absolutely everyone can now see their words in print. That has led to a radical decline in the average quality of what gets published, but it has also led to a loosening of the classic rules which shackled authors in the past. We now have the opportunity to use the full toolkit of writing tools on every writing challenge. Embrace your non-fiction with a fiction writer's mindset, carefully managing the attention and emotions of your reader, and you will deliver your argument more conclusively than with other, drier methods.
