And a radical one at that.
"Through most of human history, love was not at all the point of marriage (maybe the gravy but not meat and potatoes)," says Coontz, "Marriage was about getting families together, which was why there were so many controls."
The notion that a couple would marry for love was considered almost anti-social, even subversive; parents could disown their kids for doing it.
"The Greeks thought lovesickness was a type of insanity, a view that was adopted by medieval commentators in Europe. In the Middle Ages, the French defined love as a 'derangement of the mind' that could be cured by sexual intercourse, either with the loved one or with a different partner," Coontz writes in her 2005 book, "Marriage, A History: From Obedience to Intimacy, or How Love Conquered Marriage." "As late as the 18th century the French essayist Montaigne wrote that any man who was in love with his wife was a man so dull that no one else could love him."
Couples wed to make political alliances, to raise capital, to expand the workforce and for a whole array of practical purposes.
"Too much love was thought to be a real threat to the institution of marriage," she says in an interview. "Earlier proponents of marriage were as horrified by the idea of a love match as late 20th-century people were by idea of same-sex marriage."
Physical attraction between two people has existed as long as marriage, explains Don Herrin, who teaches a course on "family belief systems," at the University of Utah, but how that is expressed or controlled varies from culture to culture. So does the relationship of parents to children.
The women of the Tibetan Na people have sex with men from a neighboring village to get pregnant, but rear the children themselves, with the help of their brothers, he says. There are no active fathers.
And there are tribal societies in which the kids belong to the whole community, not to a set of parents, Herrin says. "Some moms are bearers and some are feeders."
Love is inherent in being human and these groups have that, he says. It just takes a different form.
Of course, polygamy is the planet's most enduring form of marriage.
"If you really want to go traditional," he says, "let's legalize polygamy."
From the first couple • You could say that the biblical Adam and Eve had an "arranged marriage" that is, a spouse they didn't choose for themselves.
The Bible does speak of love matches, of course, but those are not all monogamous think Jacob and Rachel, and her older sister, Leah. Kings David and Solomon were said to have scores of wives.
Figures in that Judeo-Christian text, like most preindustrial people, were very concerned with fertility. They slept with servants to get an heir or renounced their wives to take a separate wife or a concubine.
"It was considered part of the way the Old World operated," Coontz says. "You had to have babies."
Jesus Christ uttered little about marriage, but what he said, according to Christian scriptures, was "radically egalitarian," Coontz says. "He was interested in women as potential recruits to his movement and marriage would tie them down. He didn't condone divorce or extramarital affairs, but it didn't concern him."
For hundreds of years, marriage was a family affair, but in the later Christian era, it became about politics, property and posterity.
"If you could decide who could and couldn't marry," she says, "that was a lot of power so governments and religions were very interested in controlling it."
Again, love had little to do with it, which more often was associated with extramarital relations.
"Courtly love," which flourished among royalty in Europe from A.D. 1300 to 1500 was directed toward mistresses, Coontz says. "Love was such a transitory feeling, you couldn't truly love anyone unless it was adulterous."
The ideal of love as a primary reason for marriage began to spread in the late 18th century and early 19th century, partly due to the French and American revolutions.
Enlightenment thinkers in this era were promoting the "right to personal happiness," she says.
Jane Austen, writing in the early 19th century, raised the question in her novels: Which is worse a marriage with money but no love or marriage with love but no money?
"Somehow, her heroines always managed to fall in love," Coontz says, "with the guy with the money."
Eventually, the development of a wage labor economy moved coupling away from economics. Women didn't have to depend on their parents' ability to put up a dowry, and men didn't have to wait for their inheritance. Families moved away from farms into urban settings, so they didn't need so many children. More options opened up.
That created a sea change for marriage in the mid 19th century, including the possibility of unions founded on love, Coontz says. "We convinced ourselves that was the traditional ideal."
The postwar model • The most "marrying time in American history" was just after World War II, she says. "More women could stay at home full time, while their husbands supported them."
That was built on a combination of rising wages for men, Coontz says, and repressive laws and economics for women.
That era lasted only until the late 1960s and early '70s, when women began flocking back to the workforce.
If these "Father Knows Best" marriages represented the ideal, says Herrin, the U. professor, why did so many women flee them in the late 1970s, when no-fault divorce became available?
"Our peak years for divorce were between 1978 and 1980," he says. "Even now 67 percent of divorces are filed by women. I am sobered by that [figure]. For a lot of folks, marriage is a better relationship for guys than women."
Today, Herrin says, romantic unions have become the ideal, but not all of them are between heterosexual, married couples with children. Many prefer cohabiting to marriage and do not plan to produce offspring.
Unlike earlier eras, these days Cupid's arrow the ineffable nature of attraction is considered essential to finding a partner. You don't have to have the approval of family, faith or society. You can write your own promises, make your own money, and chart your own future.
That's the easier part, Herrin says. Making it last as a satisfying partnership is tougher.
Contemporary families are, indeed, falling apart, says the professor who teaches a class on "strengthening the family," and not because women work outside the home or gays are getting married.
It's because young lovers don't have the skills the will and commitment to clean up the wife's vomit, listen to the husband's endless fascination with football, stay by her side when she gets fired, when he has Alzheimer's, when they lose a child to turn the initial spark into a deeper burning.
Love, he says, has a lot to do with that.
Adam & Eve, husband & wife
"And the rib, which the Lord God had taken from man, made he a woman, and brought her unto the man.
"And Adam said, This is now bone of my bones, and flesh of my flesh: she shall be called Woman, because she was taken out of Man.
"Therefore shall a man leave his father and his mother, and shall cleave unto his wife: and they shall be one flesh.
"And they were both naked, the man and his wife, and were not ashamed."