At the heart of our public morality is the idea that he who gives generously is most virtuous and morally praiseworthy; that there is no greater citizen than she who sacrifices; and that there is no greater measure of worth than contribution. These are values we can be proud of. After all, there is no moral system or religion on earth where the guiding ethic is grab more for yourself.

What does purpose mean? It means the deepest desire for our short lives to mean something. . . . To speak a language of purpose is to return to first principles and to be able to answer, in plain English, the plain questions of Why? Why should we chip in to help someone else? Why should we defer gratification? Why should we care about the long term? Why should we trust anyone who seems to be limiting our ability to do what we want?

If half-black Barack Obama had decided years ago to call himself white - which his genes certainly entitled him to do - his story would have carried very different meaning. If millions of part-black people had followed him into whiteness, then the N.A.A.C.P. would be in true crisis.

I had heard so much negative talk about our generation, that we're slackers and young fogies, that I knew wasn't true of the people I know.

Identity in America is complicated but it's also simple: it's about whom you identify with and who identifies with you.

Today's multiracial Americans are at greater liberty to choose how they'd like to be seen, and under less pressure to pass for white.

Here's a proposal, offered only partly in jest: no resident of the United States, whether born here or abroad, should get to be a citizen until age 18, at which time each such resident has to take a test.