Traditionally, psychology has been the study of two populations: university freshmen and white rats.

Families survive the terrible twos because toddlers aren't strong enough to kill with their hands and aren't capable of using lethal weapons.

Because of empathy, we care more for, and devote far more resources to, someone who is familiar, from our country or our group, than a stranger.

People differ in where they direct their empathy and their compassion. Many people are intensely concerned about the suffering of non-human animals, and some do not care at all. There are cultural differences.

When people want to inspire you to turn against some group of people, they'll often use empathy. When Obama wanted to bomb Syria, he drew our attention to the victims of chemical warfare. And in both of the Iraq wars, politicians said, "Look at the horrific things that are happening." I'm not a pacifist. I think the suffering of innocent people can be a catalyst for moral action. But empathy puts too much weight on the scale in favor of war. Empathy can really lead to violence.

The fact that something can be used for good isn't necessarily a knockdown argument for it.

For the most part, people use "empathy" to mean everything good. For instance, many medical schools have courses in empathy. But if you look at what they mean, they just want medical students to be nicer to their patients, to listen to them, to respect them, to understand them. What's not to like? If they were really teaching empathy, then I'd say there is a world of problems there.