I think that communism was a major force for violence for more than 100 years, because it was built into its ideology - that progress comes through class struggle, often violent.

As women are empowered, violence can come down, for a number of reasons. By all measures, men are the more violent gender.

Violence and religion have often gone together, but it's not a perfect correlation, and it doesn't have to be a permanent connection, because religions themselves change.

The reason I'm not a neurobiologist but a cognitive psychologist is that I think looking at brain tissue is often the wrong level of analysis. You have to look at a higher level of organization.

The main reason that violence correlates with low socioeconomic status today is that the elites and the middle class pursue justice with the legal system while the lower classes resort to what scholars of violence call “self-help.

We need to spread out now in the universe. I think in 100 years we'll be living on other planets.