Read the excerpt from "A Quilt of a Country." America is an improbable idea. A mongrel nation built of ever-changing disparate parts, it is held together by a notion, the notion that all men are created equal, though everyone knows that most men consider themselves better than someone. "Of all the nations in the world, the United States was built in nobody's image," the historian Daniel Boorstin wrote. That's because it was built of bits and pieces that seem discordant, like the crazy quilts that have been one of its great folk-art forms, velvet and calico and checks and brocades. Out of many, one. That is the ideal.

The reality is often quite different, a great national striving consisting frequently of failure. Many of the oft-told stories of the most pluralistic nation on earth are stories not of tolerance, but of bigotry. Slavery and sweatshops, the burning of crosses and the ostracism of the other. Children learn in social-studies class and in the news of the lynching of blacks, the denial of rights to women, the murders of gay men. It is difficult to know how to convince them that this amounts to "crown thy good with brotherhood," that amid all the failures is something spectacularly successful. Perhaps they understand it at this moment [in the aftermath of 9/11], when enormous tragedy, as it so often does, demands a time of reflection on enormous blessings.

Which statement best traces the development of a central idea from one paragraph to the next?