Understatement deliberately expresses an idea as less important than it actually is, either for ironic emphasis or for politeness and tact. When the writer's audience can be expected to know the true nature of a fact which might be rather difficult to describe adequately in a brief space, the writer may choose to understate the fact as a means of employing the reader's own powers of description. For example, instead of endeavoring to describe in a few words the horrors and destruction of the 1906 earthquake in San Francisco, a writer might state:

• The 1906 San Francisco earthquake interrupted business somewhat in the downtown area.

The effect is not the same as a description of destruction, since understatement like this necessarily smacks of flippancy to some degree; but occasionally that is a desirable effect. Consider these usages:

• Henry and Catherine were married, the bells rang, and everybody smiled . . . . To begin perfect happiness at the respective ages of twenty-six and eighteen is to do pretty well . . . . --Jane Austen
• Last week I saw a woman flayed, and you will hardly believe how much it altered her person for the worse. --Jonathan Swift
• You know I would be a little disappointed if you were to be hit by a drunk driver at two a.m., so I hope you will be home early.

In these cases the reader supplies his own knowledge of the facts and fills out a more vivid and personal description than the writer might have.

In a more important way, understatement should be used as a tool for modesty and tactfulness. Whenever you represent your own accomplishments, and often when you just describe your own position, an understatement of the facts will help you to avoid the charge of egotism on the one hand and of self-interested puffery on the other. We are always more pleased to discover a thing greater than promised rather than less than promised--or as Samuel Johnson put it, "It is more pleasing to see smoke brightening into flame, than flame sinking into smoke." And it goes without saying that a person modest of his own talents wins our admiration more easily than an egotist. Thus an expert geologist might say, "Yes, I know a little about rocks," rather than, "Yes, I'm an expert about rocks." (An even bigger expert might raise his eyebrows if he heard that.)

Understatement is especially useful in dealing with a hostile audience or in disagreeing with someone, because the statement, while carrying the same point, is much less offensive. Compare:

• The second law of thermodynamics pretty much works against the possibility of such an event.
• The second law of thermodynamics proves conclusively that that theory is utterly false and ridiculous.

Remember, the goal of writing is to persuade, not to offend; once you insult or put off your opponent, objector, or disbeliever, you will never persuade him of anything, no matter how "obviously wrong" he is or how clearly right you are. The degree and power of pride in the human heart must never be underestimated. Many people are unwilling to hear objections of any kind, and view disagreement as a sign of contempt for their intellect. The use of understatement allows you to show a kind of respect for your reader's understanding. You have to object to his belief, but you are sympathetic with his position and see how he might have come to believe it; therefore, you humbly offer to steer him right, or at least to offer what you think is a more accurate view. Even those who agree with you already will be more persuaded because the modest thinker is always preferable to the flaming bigot. Compare these statements and consider what effect each would have on you if you read them in a persuasive article:

• Anyone who says this water is safe to drink is either stupid or foolish. The stuff is poisoned with coliform bacteria. Don't those idiots know that?
• My opponents think this water is drinkable, but I'm not sure I would drink it. Perhaps they are not aware of the dangerous bacterial count . . . [and so on, explaining the basis for your opinion].