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Each week, In Theory takes on a big idea in the news and explores it from a range of perspectives. This week we’re talking about singlehood in America. Need a primer? Catch up here.

Stephanie Coontz is director of research at the Council on Contemporary Families and author of the forthcoming revised edition of “The Way We Never Were: American Families and the Nostalgia Trap.”

Over the ages, some societies have accorded far less value and respect to singles than to married individuals. In Colonial America, unmarried men and women were never considered full adults, no matter how old they were. And in the 1950s, psychologists labeled unmarried men “deviant,” “infantile” or even “pathological,” while single women were seen as “neurotic,” “unnatural” and “castrating.”

[Other perspectives: Why it’s time to stop glorifying marriage]

But Supreme Court Justice Anthony Kennedy was wrong when he claimed in his eloquent but historically flawed majority decision on marriage equality that marriage has everywhere embodied “the highest ideals of love, fidelity, devotion, sacrifice, and family,” conferring “nobility and dignity” on those who enter it.

To Hindus, marrying was a holy act and an unmarried person was considered impious, but in the Christian tradition, the highest status went to those who chose celibate single lives. In the hierarchy of Catholic womanhood, the virgin ranked first, the widow ranked second, and the wife came in last. In medieval Europe, thousands of unmarried women lived out their lives communally in convents or in lay co-housing communities. Aristocratic families often pushed their younger sons into monasteries or into military service with distant allies to avoid having them marry and cut into the eldest son’s inheritance.

Whatever their relative valuation of the single and married states, most societies in history made sharp distinctions between those who married and those who remained single: They were seen as mutually exclusive ways of life, with different legal rights and social obligations. Yet today, the line between singlehood and marriage has been blurred. It’s time to reconsider the way we look at both.

With the rise of cohabitation, most marriages now involve people already living together. On the other hand, many single individuals bear and raise children by themselves. Prolonged solo living is on the rise even among those who will eventually marry, and some researchers believe that a quarter of today’s young adults will reach their mid-40s without ever having married.

But the rise of lifelong singlehood and the eclipse of marriage have been greatly exaggerated. Most people eventually marry, even those who reach an age at which they would once have been permanently assigned to the singles category. In 2013, more than 80 percent of 50-year-olds — people who went to high school in the already marriage-skeptical 1980s — were married. And those who were still unmarried at age 50 had much better prospects for eventually marrying, should they want to, than in the past.

Given the increased spread in age at first marriage, it is projected that about 85 percent of white women and 78 percent of black women will have been married at some point by the time they reach age 85. While this is lower than the 96 percent of white and 91 percent of black women who were ever married by age 85 in 2010, it certainly indicates that marriage is not on the verge of extinction.

But marriage is also not the all-encompassing and undeviating state that it used to be. Many people who eventually wed will still spend more than half their adult lives as singles, bringing the habits and networks formed during those years into their marriages. And once married, they seldom assume that coupledom is a permanent state, around which they can organize their entire identity. About 40 percent of marriages seem destined to end in divorce, despite the decline in the divorce rate since 1979.

With that rate high and remarriage rates falling, many Americans become single again after 10 or 15 years of marriage. Even older Americans in long-term marriages increasingly reenter singledom. The divorce rate of people age 50 and over has doubled since 1990, and the rate for people 65 and older has tripled. Today, 1 in every 4 people who divorces is over age 50 and nearly 1 in 10 is 65 or older.

[Everything you think you know about single people is wrong]

Still, the Internet (combined with the extension of the active lifespan) offers older individuals far greater opportunities to find new romantic partners if they wish. The proportion of older adults living together without marrying  has increased fourfold since the 1960s, and even those who live alone are far more likely to cultivate their independent social networks just as never-married Americans do.

Most Americans will experience singlehood at several stages of life, during which they often adopt many of the interpersonal commitments that used to be reserved for marriage. And most married people no longer abandon the identities, habits and friendships they acquired as singles. It no longer makes sense to see singlehood and marriage as two distinct and stable social categories that should be accorded different legal rights and social esteem.

Explore these other perspectives:

Bella DePaulo: Everything you think you know about single people is wrong

Sarah Wright: Why it’s time to stop glorifying marriage.

Eve Tushnet: Being single shouldn’t mean being alone

Michael Cobb: Advertisers want you to hate being single. Don’t buy in.

Naomi Schaefer Riley: The dangers of celebrating single motherhood