A medieval canon of sin takes no account of modern actions the Vatican calls sinful, such as genetic manipulation.

Editorial Observer/EDUARDO PORTER

It’s hard to erect rules to last forever. The recent suggestion by a bishop from the Vatican’s office of sin and penance that globalization and modernity gave rise to sins different from those dating from medieval times seemed to many like an acknowledgment that the world is, indeed, changing.
Norms encoded hundreds of years ago to guide human behavior in a small-scale agrarian society could not account for a globalized postindustrial information economy. Polluting the environment, drug trafficking, performing genetic manipulations or causing social inequities, new sinful behaviors mentioned by Monsignor Gianfranco Girotti, regent of the Vatican Penitentiary, are arguably more relevant to many contemporary Catholics than contraception.
“If yesterday sin had a rather individualistic dimension, today it has a value and resonance that is above all social, because of the great phenomenon of globalization,” Monsignor Girotti told the newspaper L’Osservatore Romano.
Sin, however, doesn’t take well to tinkering. Many Catholic thinkers reacted strongly against the idea that new sins were needed to complement, or supplement, the classical canon. They accused the press of exaggerating Monsignor Girotti’s words. Their reaction underscored how tough it is for the church to manage a moral code grounded in eternal verities at a time of furious change.
The Vatican has long been riven by this tension between dogma and the outside world. Yet it could apply to any religion: it’s hard to rejigger the rules when truth is meant to be fixed forever. The core benefits of religions, unlike other, worldly institutions, often relate to the afterlife. Some social scientists argue, however, that many benefits of church membership are to be had this side of death. The gains are not unlike the advantages of a club of like-minded people. Religions provide rules to live by, solace in times of trouble and a sense of community. Some economic studies suggest that this can promote higher levels of education and income, more marriage and less divorce.
Such a club needs strong, believable rules. Like marriage, membership will be more valuable the more committed the other participants are to the common cause. Demanding rules - say celibacy, or avoiding meat during Lent - help enhance the level of commitment.
Strict rules, says the Nobel-winning economist Gary Becker, screen out free riders who wish to enjoy the benefits of membership but are unwilling to invest the necessary zeal in the enterprise. Rules provide commitment devices - like 10-point plans to stop drinking. And they tie members closer by substituting taboos - like drinking and dancing - with acceptable activities, like prayer or Sunday school.
Larry Iannaccone, an economist at George Mason University in Virginia who has studied religions, notes that some of the most successful, like Jehovah’s Witnesses or Pentecostal Christians, which have very fervent congregations, have strict requirements. Religions relax the rules at their own peril.
“Religions are in the unusual situation in which it pays to make gratuitously costly demands,” Mr. Iannaccone said. “When they weaken their demands they make on members, they undermine their credibility.”
The Vatican is particularly attentive to these strictures. Catholicism has lost sway in many parts of the world. Only 24 percent of American adults identify with the church, though more than 31 percent say they were raised Catholic. In Italy, only about one in four respondents to a 2002 poll said religion was very important.
Many traditionalists attribute the church’s decline to the weakening of its strictures. They believe it was damaged by the Second Vatican Council in the 1960s, which tried to bring the church closer to the people, proclaimed religious freedom, embraced people of other Christian faiths and acknowledged truth in other religions.
So it is perhaps unsurprising that the church has been pushing the other way. Pope Benedict XVI has brought back rites abandoned after Vatican II and reasserted the church’s hold on truth.
In this context, it could be tricky to update sins in a way that could de-emphasize individual trespasses and shift the focus to social crimes bearing a collective guilt. New sins might be a better fit for the modern world, but they risk alienating the membership.