Despite all the contention, violence, and chaos in the world today, the good news is that humans, overall, are getting better at tolerance and empathy. We’re allowing more people into our “in-group” and excluding fewer. We seem to be rising above our tendency to put everyone into “us” and “them” buckets, with fewer exceptions.

But as this Nautilus article explains, we’ll never reach a point where everyone is “us.” There will always be a “them”—like Democrats and Republicans, Sunnis and Shiites, Duke and North Carolina basketball fans. We can try to overcome our biases, but “universal empathy” just can’t happen.

Adam Waytz, a social psychologist and professor at Northwestern University’s Kellogg School of Management, explains:

“Social scientists have found that in-group love and out-group hate originate from the same neurobiological basis, are mutually reinforcing, and co-evolved—because loyalty to the in-group provided a survival advantage by helping our ancestors to combat a threatening out-group. That means that, in principle, if we eliminate out-group hate completely, we may also undermine in-group love. Empathy is a zero-sum game. Absolute universalism, in which we feel compassion for every individual on Earth, is psychologically impossible.”

Maybe it is impossible, but still, it’s a noble goal worth reaching for.