Separate paragraphs should not be made of matter which belongs together. If the ideas can all be fairly included under one general topic, unity demands that they be grouped in one paragraph. Thus, in describing the route followed in a certain journey, one should not use a separate paragraph for each step in the journey.
Wrong:
In returning to the University, I went from Pittsburgh to Cleveland.
Then I took a berth for the night on one of the lake steamers running from Cleveland to Detroit.
From Detroit I completed the journey to Ann Arbor on an early train the next morning.
If unity is to be secured, not only must all the ideas brought out in the paragraph deal with the same topic, but also, they must be developed in some consistent, systematic order. A certain point of view should be generally maintained as to tense, subject, and manner of expression.
147. How to Gain Unity. Careful thought before beginning the paragraph is necessary if unity is to be gained. The topic of the paragraph should be determined, and should be clearly indicated by a topic sentence. Usually this topic sentence should be placed near the beginning of the paragraph. The first sentence is the clearest and best place for it. The topic sentence need not be a formal statement of the subject to be discussed, but may be any sentence that shows what is to be the central idea of the paragraph.
With the topic determined, there are various ways of developing it. It may be developed by repetition; by adding details and specific instances to the general statement; by presenting proof; by illustration; or by showing cause or effect.
148. Examine the following paragraphs. Each possesses the quality of unity. The topic sentence in each case is italicized.
To rule was not enough for Bonaparte. He wanted to amaze, to dazzle, to overpower men's souls, by striking, bold, magnificent, and unanticipated results. To govern ever so absolutely would not have satisfied him, if he must have governed silently. He wanted to reign through wonder and awe, by the grandeur and terror of his name, by displays of power which would rivet on him every eye, and make him the theme of every tongue. Power was his supreme object; but power which should be gazed at as well as felt, which should strike men as a prodigy, which should shake old thrones as an earthquake, and, by the suddenness of its new creations, should awaken something of the submissive wonder which miraculous agency inspires.