Liberalism cannot easily renew itself, because despite what certain of its detractors and some of its champions insist, it isn’t really a political-moral-theological system in full; rather, it’s a deliberately thinned-out structure designed to manage pluralism, which depends on constant infusions from other sources, preliberal or nonliberal, to generate meaning and energy and purpose. There are moments of transition and turmoil when liberalism appears to stand alone, and liberals sometimes confuse these moments for an aspirational norm. But nobody except Hugh Hefner, Gordon Gekko and a few devotees of the old A.C.L.U. can bear to live for very long under conditions of pure liberalism. Instead, the norm for successful societies and would-be society builders is liberalism-plus: liberalism plus nationalism (as in 19th-century Europe or Ukraine today), liberalism plus intense ethnic homogeneity (the Scandinavian model, now showing signs of strain), liberalism plus mainline Protestantism (the old American tradition), liberalism plus therapeutic spirituality (the mode of American culture since the 1970s), liberalism plus social justice progressivism (the mode of today’s cultural left), etc., etc. Something must be added, some ghost needs to inhabit the machine, or else society begins to resemble the portraits painted by liberalism’s enemies — a realm of atomized, unhappy consumers, creatures of self-interest whose time horizons for those interests are always a month rather than a decade, Lockean individuals moving in a miserable herd.