Splitting is a defense mechanism by which people unconsciously frame ideas, individuals or groups of people in all-or-nothing terms—for example, all good or all bad. The term was popularized in its current usage by the psychoanalyst Melanie Klein in the 1930s and ’40s. Its name describes how intolerable thoughts and feelings are split off from the subject’s awareness, leading to a partial view of the world. To see our opponents as pure evil, we have to split off the parts of them that are admirable. To see ourselves as purely righteous, we have to split off our shortcomings.
Hartz argues that this explains polarization. We learn to tune out any sort of positive perceptions of people whose political views differ from ours.
I think of splitting as another term for, or at least related to, cognitive dissonance. Believing something good about someone who disagrees with you creates cognitive dissonance. The easiest way to resolve that is to avoid believing something good about someone who disagrees. In The Three Languages of Politics, I call this the need for closure.