It is hard to think of a notion more popular today than diversity. Monoculture is out. Multiculturalism is in. Uniform social groups are at best regarded as boring, and sometimes even regarded suspiciously. Diverse social groups, companies, universities, and churches are esteemed.

I live in Berkeley, California and teach at the University of San Francisco, one of the most ethnically diverse universities in the country. In the San Francisco Bay Area, diversity has become a kind of quasi-religion, a value that seems to hold a trump card over competing values. For this reason there is a tendency, especially among conservatives, to react against diversity. And as an economist, I have often wondered whether the main achievement of diversity stops at the warm fuzzies it seems to create inside many of its believers, or whether behind it there is something more substantial, more fundamental. I believe there is.

The Apostle Paul had much to say about diversity in the church. In the twelfth chapter of his first letter to the Corinthians, Paul uses the analogy of a body with many parts to describe the early Christian church. Each member is an eye, an ear, a hand, a foot, and complements the other parts of the body. This is a concept economists can latch onto as we are in the habit of categorizing things as substitutes and complements. Substitutes are like two different kinds of cookies, while examples of complements are, say, milk and cookies.

What Paul is saying makes eminent sense to a hard-nosed economist. A body of people with the same backgrounds, insights and skills is a weaker body than one with a diverse set of backgrounds, insights, and skills. Why? Because the parts of the diverse body complement one another, while the parts of the homogeneous body are substitutes. As a result, the added value of the 250th musician to the group is virtually nil. Diminishing returns have long set in.

The church to which my family in Berkeley belongs is diverse. We have old people, young people, black people, Latinos, Asians, rich people, poor people, physically and mentally disabled people and lots of babies. However, a couple of years ago, I was on sabbatical for a year in the economics department at the University of California at Santa Barbara. There we attended a sister church in our denomination, but one that was much more homogeneously white and prosperous. Moreover, the church seemed to consist almost solely of young families. It was almost as if one needed to be holding the hand of a toddler to be admitted through the front door.

While we enjoyed our year there, my wife and I noticed something within the church. There seem to be a kind of subtle competition going on between members. It was a church full of "beautiful people" and each young woman seemed to be working a little too hard to stand out as attractive amongst her peers. Among the men of the congregation, type of employment, salary and home ownership seemed to establish an unspoken ladder, and yet conversations often turned to laments of one's current position on the ladder and strategies for ladder-climbing.

I am not particularly jealous of anyone in our church at Berkeley, because there are not many people like me to whom I can compare myself. In our church in Santa Barbara, everyone was like me, and so I could be ranked. In our Berkeley church, I am valued because I bring a set of insights and skills to the group that is complementary to what exists among the others. In the Santa Barbara church, because there were many others like me, my background, insights, and skills competed with what already existed. In other words, to employ my gifts in leadership (say in teaching, administration, or music) I would be need to supplant someone whose similar gift was slightly weaker than mine. Homogeneity fosters competition; diversity yields complementarity.

Social scientists tell us that much of what we understand about the world occurs through interaction in our social networks. Through the comments and insights of our peers we learn to interpret the world. Our social networks are constantly providing us with new information that guides us in our decision-making over big and small issues.

Here again, diversity dominates homogeneity. Suppose my social interaction occurs primarily among people just like me. To put it bluntly, these people are providing me with almost no new information about the world. Their backgrounds are like mine, and so the lens through which they have come to view the world is nearly the same as my own. They have similar jobs and similar types of social circles, and so any new stimulus or ideas they receive is similar to what I myself am already receiving. Their insights are often the same as my own insights, and so at some level their comments at best disinterest me (when they are correct) and at worst reinforce my own biases, prejudice and ignorance (when they are wrong).

In a heterogeneous social network, I am constantly bombarded with new information, insights and ways of viewing and addressing issues. Although it may take more effort for me to understand the perspective of someone from a different background, the end payoff is often higher.

Scott Page is Professor of Complex Systems, Political Science and Economics at the University of Michigan, and is author of The Difference: How the power of diversity creates better groups, firms, schools, and societies. The premise of his book is that diversity offers tangible benefits to group problem-solving relative to homogeneity. Many of the insights of the book are based on his problem-solving experiments.

When these experiments are undertaken individually, some high-performing individuals always do better than others. But when Page forms problem-solving groups, he finds that groups made up of individuals with heterogeneous skills almost always do better than groups of homogeneous skills. This is relatively unsurprising. But what is surprising is that groups made up of a combination of high and mediocre individual performers outperform homogeneous groups made up of only high individual performers. He concludes that one could probably do as well at solving group problems by randomly selecting problem-solving groups as by engaging in an effort to select a uniform group of only "smart" people. We can learn much about the value of diversity from this kind of research.

While we should be wary of adopting diversity as a quasi-religion that trumps all other values, we can learn much from the value it brings to friendship circles, companies, schools, and churches. Valuing diversity offers more than overcoming the guilt associated with discrimination. It appears Paul knew what he was talking about after all.