Unity.—Although thought grows, one must keep in mind that it does not always grow to fruit unless it is trained and pruned. Thought loves to branch, and unless restrained by a stern sense of logic, it will often end in a mere tangle of superfluous twigs and leaves. To speak less figuratively, every writer is in danger of setting down matters suggested by the subject in hand but not logically related to it. This is as true of a large piece of work as of a sentence (compare [page 90]). Every theme, like every sentence, should have unity. It should be the development of one idea—a large, complex idea, if you please, but, nevertheless, one. No matter how long or how short the whole, it must all concern the different phases of one thing or one thought. It should grow naturally from one germ. Every part in it should bear on the central idea of the whole—so that, after reading any given sentence, the reader can see a real connection between title and sentence. A well-organized composition cannot spare any part; each is essential to its life. Milton said, “Almost as well kill a man as kill a good book”; and we may adapt this idea to the structure of the theme. A good composition is so well organized that if you cut it anywhere it will bleed.
Planning a Paragraph.—Before writing a paragraph, try to think out the whole of it. Let the thought grow in the mind before you let it grow on paper. This method will afford a chance to review the whole mentally and to determine whether the thoughts follow each other logically.
The Topic Sentence.—When an after-dinner speaker rises to respond to a toast, he generally announces his topic at once, or after a sentence or two of introduction. He is very likely also to announce at once his chief thought about the subject; for he knows that people like to hear him come to the point. If however he has reason to think that his hearers may not agree with him immediately, he is likely to state his subject first, and then lead up gradually to his own conclusion about it.
We naturally follow some such course in writing. With each paragraph we begin a new speech, as it were. It is a matter both of courtesy and of economy if in each we state definitely what we are talking about. The topic sentence of a paragraph ordinarily states the general subject, or else declares the general thought, i.e. conclusion, of the whole. It is generally short, because emphatic.
The following paragraph shows its general subject in the opening sentence.
A Tree-Planting Association has been organized in New York City. The Association will be organized with twelve or more members on a block, who will form a local club under the Association. A tree-planting association may, in this city, fail to plant trees, but it certainly will encourage the planting of window boxes, the fencing of unused lots, the painting of fences to the exclusion of posters, and the general care of the public street. Back yards will assume some relation to the general good of the community, and trees, vines, and flowers will find place in them. The children will be taught to care for the appearance of the block, and chalk-marks and other defacements will soon disappear, because of new-born civic pride.—The Outlook.
In the following paragraph, Macaulay does not state his topic till the second sentence. The first is a general remark by way of introduction.
One of the first objects of an inquirer, who wishes to form a correct notion of the state of a community at a given time, must be to ascertain of how many persons that community then consisted. Unfortunately the population of England in 1685, cannot be ascertained with perfect accuracy. For no great state had then adopted the wise course of periodically numbering the people. All men were left to conjecture for themselves; and, as they generally conjectured without examining facts, and under the influence of strong passions and prejudices, their guesses were often ludicrously absurd. Even intelligent Londoners ordinarily talked of London as containing several millions of souls. It was confidently asserted by many that, during the thirty-five years which had elapsed between the accession of Charles the First and the Restoration, the population of the City had increased by two millions. Even while the ravages of the plague and fire were recent, it was the fashion to say that the capital still had a million and a half of inhabitants. Some persons, disgusted by these exaggerations, ran violently into the opposite extreme. Thus Isaac Vossius, a man of undoubted parts and learning, strenuously maintained that there were only two millions of human beings in England, Scotland, and Ireland taken together.—Macaulay: History of England, Chapter III.
In the following paragraph, the topic sentence states the general thought of the whole.
The appetite of this fish is almost insatiable. Mr. Jesse threw to one pike of five pounds’ weight, four roach, each about four inches in length, which it devoured instantly, and swallowed[27] a fifth within a quarter of an hour. Moor-hens, ducks, and even swans have been known to fall a prey to this voracious fish, its long teeth effectually keeping them prisoners under water until drowned.—Dr. J. G. Wood.