Roger Waters, the mastermind behind Pink Floyd’s 43-year-old and still massively popular album, “The Dark Side of the Moon,” will launch a tour called “Us + Them,” with “a story that’s about whether love trumps everything.” It is interesting that the media, including National Public Radio, have referred repeatedly to it as the “Us and Them” tour rather than as the “Us Plus Them” tour. Waters could have chosen an ampersand, but he chose a plus sign.

So did I when I published “Us Plus Them” in 2012. The book focused on the existence and tremendous promise of positive feelings about a group other than one’s own — feelings which I collectively call “allophilia.” That’s what the “plus” in the title meant. Yet the book was constantly referred to as “Us and Them” and I was frequently introduced as the author of “Us and Them,” not “Us Plus Them.”

What’s the problem with “plus”? For a university like Yale that is trying to address social diversity head on, this is actually a most instructive mistake. In its small way, the “plus” shows how hard it is for people to see “us” and “them” as anything other than natural opposites who can, at best, tolerate each other. When we read, “It’s us and them,” it almost always means, “It’s us against them.” For a long time, the idea that “us and them” could be something positive — a sum rather than a difference — was seldom taken seriously, even by social scientists.

But that’s changing. Social scientists around the world are investigating the finding that affection is not just the lack of animosity and, in fact, love and hate can coexist. So when Joni Mitchell sang, “I hate you some. I love you some,” it was a perfectly accurate observation. Still, when it comes to intergroup relations, we’re well-trained to see the dark side of diversity but much less attuned to the light side. We see the microaggressions but not the microaffirmations, although they are there. We encourage empathic sorrow, but overlook the power of empathic joy. We see the prejudice — on some days, who could miss it? — but not the allophilia.

In all these ways, we’re missing the “plus” in “Us + Them.” Not just the word, but the very human capacity to nurture positive feelings about other groups (i.e., curiosity, interest, engagement and even enthusiasm) and put them to constructive use in our communities and our politics.

In describing his goals for the tour, Waters speaks of “love” trumping everything. In a 1957 sermon, the Rev. Dr. Martin Luther King Jr. observed, “Hate cannot drive out hate; only love can do that.” Many years after King’s sermon, my own social science research and that of others are showing that allophilia has the capacity to take us beyond mere tolerance — or anti-racism — to something much more constructive, resilient, good-hearted and joyful.

At Yale and other campuses, many students can see the work to be done. That will require common cause, which comes from having positive feelings among distinct groups. The lack of prejudice is not enough; tolerance simply doesn’t motivate action and cooperation. Critiquing one another and focusing on hate runs the risk of never settling down to labor for the structural changes that will only work if most members of our community are willing to help make them work.

After 10 years of research and teaching on diversity and difference — focusing not on the source of hate but rather on the positive steps leaders can take — I am convinced that undergraduates at colleges like Yale have unique opportunities to find the light in diversity. What a shame if the conversations keep swirling around offense and never flow toward the opportunities for affinity that are so abundant for college students. And what a shame if five students write dissertations on microaggressions this year and no one writes one on microaffirmations.

Remembering my younger self in the Jonathan Edwards dining hall with people from many demographic and ideological backgrounds, I offer a suggestion: Lead with curiosity. Hear people out about how hard it can be, but don’t stop there.

Let’s not turn our backs on anything that might help us to envision and pioneer the future we want. Even if it’s just a plus sign.