Make this the test of each paragraph: if it does not illuminate the central thought, fit into the argument at that point, or add to the interest of the reader, eliminate it or bring it into conformity with the "idea behind the letter."
And there must be an actual continuity of thought from paragraph to paragraph. Merely inserting a catch-word or a conjunctive does not build a logical bridge.
The letter from another insurance agent might have been saved if this test had been applied, for it was well written except where the writer forgot himself long enough to insert an irrelevant paragraph about his personal interest:
"We are desirous of adding your name to our roll of membership because we believe that every man should be protected by insurance and because we believe this is the best policy offered. We are endeavoring to set a new record this month and are especially anxious to get your application right away."
* * * * *
The continuity of thought is broken. The preceding paragraphs have been working up the reader's interest in casualty insurance by pointing out the dangers to which he is exposed, the humiliating position in which it will place him and his family to be the recipients of charity in case of sickness or accident, and so on. Then the writer short-circuits the reader's interest by a paragraph of generalities which call attention to his desire for profits— things in which the prospect is not interested.
Most propositions can be developed in different ways, along different angles. The problem of the correspondent is to determine upon the way that will prove easiest for the reader to follow. He may have his path smoothed for him if he understands how facts, ideas and arguments will cohere in the reader's mind. It is much easier to follow a proposition if it is developed along some definite channel; if it follows the law of continuity, the law of similarity; of association or contrast, or of cause and effect.
Some epigrammatic thinker once said, "When you get through, stop!" This applies to letter writing as well as to speech. But don't stop a letter on the down grade. Stop after you have given your hardest punch. This is what rhetoricians call the climax.
A letter constructed along these principles of style will almost inevitably have a climax. If there is an idea behind the letter, if it is carried out logically, if the letter sticks to this one idea, if the argument is carried along step by step, proceeding from the general statement to the specific, from the attention-getting first sentence to the inducement, then you are working up your reader's interest to the point where with one final application of your entire idea to his own individual case, you have accomplished your climax, just as was done in the re-written letter about gasoline engines.
A letter from a firm manufacturing a duplicating machine starts out by calling attention to the difficulty the personal salesmen has in getting an audience with the busy executive. The second paragraph shows how his time and "your money" is wasted in call-backs and in bench warming while the solicitor waits for an opportunity to be heard. The third paragraph tells how over-anxious the salesman is to close a sale when a few minutes is granted—and usually fails, at least the first time. The fourth paragraph shows how this costly process of selling can be reduced by using the mails; then follow a couple of specific paragraphs telling about the advantage of the company's machine. A paragraph on the saving on five thousand circulars that would pay for the machine brings the proposition home to the reader and then, with interest at the height, the last paragraph—the climax—urges the reader to fill out a post card to secure the additional information regarding capacity, quality of work and cost. Logic, unity, sequence, climax—each does its part in carrying the load.