In 1916, a young advertising man called Oliver Adams visited a paper mill outside New York City. He spent two days walking the plant, watching the process, taking notes. He discovered that the paper was made from carefully selected white rags, that it was dried in a clean loft, that it was inspected by hand, sheet by sheet. He wrote these facts down and built an advertising campaign around them.

The manufacturer, a man called Merritt, was not impressed. "Every good bond paper is made of carefully selected rags," he said, quoting Adams's own copy back at him. "Every good bond paper is made with pure filtered water. All good papers are hand inspected." He had been making paper for twenty years. These were not revelations. These were the basic facts of his trade.

Adams looked at him steadily. "Mr. Merritt," he said, "to whom are you advertising — paper-makers or paper-users?" Merritt went quiet. Then he signed the contract. The campaign was a success. The lesson is simple in retrospect, and almost no one applies it.