Psychologists know that having political views that strongly oppose others’ has a gratifying and rewarding effect. It gratifies us because it allows us to feel as though we’re part of a team. It feels good for the simple reason that it helps us to feel connected and forget ourselves for a period of time—we become immersed in something larger. But at its most extreme, partisanship becomes psychologically addictive. It leads to fundamentalism and blind, unquestioning faith. This is the dark side of strong conviction.