Earlier quoted context omitted.
Regardless of how a person votes, they're voting for a feel-good reason. Some people's identity gives them pleasure in voting for the candidate that rationally maximizes the Good, for some subjective measure of the good. These are the 'social preferences' Gellman talks about. Some people's identity gives them pleasure in the tribe, and they want to vote for the people like them and around them to fit in, especially s…
> Pretty much everyone has both tendencies, which are inherently in tension. This is cognitive dissonance. People don't like experiencing this, so they end up choosing to believe both in tribal politics and that their tribe is the rational one, which is the most convenient way to cut that Gordian knot. And in addition, the more and more fiercely we tribally associate, the less and less we want to do with the other tr…
The current extreme polarization in the US is new and fairly unusual, in historical terms. It could be an inevitable phase that other counties will reach too, or it could just be a random artifact of the US's history and political system. Very few countries have a voting system that locks in the main two parties as strongly as the US, for example.
The idea that all politics is purely about tribal identity, and that "rationality" is a myth, would seem to suggest that we've never made any real social advances. But I'd count things like the outlawing of slavery as advances.
It reminds me of the extreme view of social structures in science (which Thomas Kuhn subscribed to, if I remember right), that all scientific "advances" and "revolutions" are just changes in fashion as one generation of scientists succeeds another. But each advance does in fact get us closer to the truth, even if we never quite reach it.