The concept of marriage as a union of a man and a woman in lifetime partnership is thousands of years old. But as long as people have been getting married, there have been divorces, or other legal ways to end marriages. Though legal in most societies, divorce has often been frowned upon. Until recent decades, divorce was frequently viewed as abnormal or wrong. Since the 1970s, divorce rates have risen steadily. In 2000, 49 percent of U.S. marriages ended in divorce. Although there were over twenty million divorced people in the United States in 2000, American society still worries about whether divorce is a selfish act of people not willing to try hard enough to create a successful marriage or a positive step to end an unhappy relationship.

In many early cultures, marriage was a civil or a legal contract, and divorce was also purely a matter of law. Ancient...