But the millennials’ skepticism of parties, programs and people runs deeper than their allegiance to a particular ideology. Their left-wing commitments are ardent on a few issues but blur into libertarianism and indifferentism on others. The common denominator is individualism, not left-wing politics: it explains both the personal optimism and the social mistrust, the passion about causes like gay marriage and the declining interest in collective-action crusades like environmentalism, even the fact that religious affiliation has declined but personal belief is still widespread.

So the really interesting question about the millennials isn’t whether they’ll all be voting Democratic when Chelsea Clinton runs for president. It’s whether this level of individualism — postpatriotic, postfamilial, disaffiliated — is actually sustainable across the life cycle, and whether it can become a culture’s dominant way of life.

One can answer “yes” to this question cheerfully or pessimistically — with the optimism of a libertarian who sees such individualism as a liberation from every form of oppression and control, or the pessimism of a communitarian who sees social isolation, atomization and unhappiness trailing in its wake.

But one can also answer “no,” and argue that the human desire for community and authority cannot be permanently buried — in which case the most important question in an era of individualism might be what form of submission it presages.