If you want to write a good sentence, you must learn to love the period. Love it above all other punctuation marks, and see it as the goal towards which the words in your sentence adamantly move.
A sentence, once begun, demands its own completion. As pilots say: take-off is optional, landing is compulsory. A sentence throws a thought into the air and leaves the reader vaguely dissatisfied until that thought has come in to land.
We read a sentence with the same part of our brains that processes music. Like music, a sentence arranges its elements into an order that should seem fresh and alive and yet shaped and controlled. A good sentence will often frustrate readers just a little, and put them faintly on edge, without ever suggesting that it has lost control of what is being said. As it runs its course, it will assuage some of the frustration and may create more. But by the end, things should have resolved themselves in a way that allows something to be said.
Only when the full stop arrives can the meaning of a sentence be fulfilled. The period offers the reader relief, allowing her to close the circle of meaning and take a mental breath.
Periods also give writing its rhythm. They come in different places, cutting off short and long groups of words, varying the cadences—those drops in pitch at the sentence’s end which signal that the sentence, and the sentiment, are done.
A sentence wields more power with a strong stress at the end, where it sticks in the mind and sends a backwash over the words that went before. Weak sentences have weak predicates that come to the period with an unresounding phhtt. If you say that something is “an interesting factor to consider” or “should be borne in mind,” then the end of your sentence is just mumbly noise, because those things could be said about anything. A sentence with a strong end-stress says that its maker cared how its words fell on the reader’s ear. It feels fated to end thus, not just strung out to fill the word count.
A good trick, when drafting a piece, is to press enter after every sentence, as if you were writing a poem and each period marked a line break. This renders the varied (or unvaried) lengths of your sentences instantly visible. And it foregrounds the period, reminding you of its power as the destination and final rest of each sentence. Winston Churchill wrote his speeches like this, in single-sentence lines, to more easily adjust his Augustan rhythms. If you keep pressing enter after every period, the music of your writing is easier to hear because now it can also be seen.
We live in an age when the period is losing its power. The talky, casual prose of texting and online chat often manages without it. A single-line text needs no punctuation to show that it has ended. Instead of a period, we press send. Omitting the period gives off an extempore air, making replies seem insouciant and jokes unrehearsed.
But writing is not conversation, nor a speech-balloon text awaiting a response. A written sentence must give words a finished form that awaits no clarification. It must be its own small island of sense, from which the writer has been airlifted and on which no one else need live. We write alone, as an act of faith in words as a way of speaking to others who are elsewhere. So a sentence must be self-supporting. It must go out into the world without the author leaning over the reader to clarify its meaning. Hence the period.
A sentence is also a social animal; it feeds off its neighbours to form higher units of sense. It needs a period not just to be a sentence, but so the next one can begin. Studies have shown that young people tend to read a full stop in a text as curt or passive-aggressive. On social media, a full stop is often used between every word to sound angrily emphatic: End. Of. Story. But in writing, a full stop is not meant to be the final word in an argument like this. It is a satisfying little click that moves the dial along so the next sentence can pick up where it left off. Its end is also a beginning.