Under ordinary circumstances, the institutions built by the old are repopulated by the young, who adjust them for new circumstances but leave them basically the same, in turn handing them over to the next generation. The possibility of successful passage through the institutions of society is what makes a person follow a normative rather than deviant life course: being a woman or a man roughly the way she or he is supposed to, partnering and reproducing in the socially standard fashion, trying to get ahead or at least get by according to prevailing ethics of education and work. In our society, this has meant (in ideal-typical middle-class terms) homeownership, an occasional vacation, sending your kids to college, and retirement. Historical continuity—the integrity of social institutions over time—works itself out on the individual level: people may feel they are making distinct, agonizing life choices, but for the most part they are living out those institutions predictably. An institution is, at the end of the day, just a pattern of social behavior repeated long enough. On the other hand, if the institutions aren’t processing enough people into the proper form—if too many can’t or won’t do family, school, work, and sex approximately the way they’ve been done before—then large-scale historical continuity can’t happen. The society can’t look tomorrow like it does today.