Yeah, I think it’s the two things you say (technology leading to filter bubbles + toxoplasma). You mention it indirectly, but I also want to explicitly point at the role, prior to the internet, that mass media had in shaping a common narrative that people could refer back to.
At the risk of substituting an elegant model for a more complicated multi-causal one, here are a few other forces that come to mind as well...
The World Wars and the Cold War gave the US powerful, external enemies, which does wonders for internal unity.
I think the 2-party system also plays a role; my impression is that polarization seems a bit less intractable in countries with multi-party systems, because when parties have to form coalitions to get things done, that affects the way the people who identify with those different parties feel about each other.
I don’t think tight control by a single political faction is the only possible fix (if you can even call that a fix!). I think on the extremely unlikely end, you could have some kind of national education reform that brings tools for productively resolving disagreements, like double crux, into public schools . If you want something less unlikely, then voting reforms that break the current 2-party duopoly, such that we move toward proportional representation or approval voting, could also have beneficial effects on polarization.
Finally, there’s the possibility of another external threat, preferably one that is actually grounded in reality, one that’s worth fighting. One might have hoped catastrophic risks like pandemics could have served this purpose, but we see how that went this time around. Unfortunately humans are hard-wired to see other humans as the most valid kind of threat.
I want to throw in one last note of caution against overstating current levels of polarization and division, because it’s too easy to see the past as better than it actually was. When I think of divisive elections, I also think back to the Jefferson-Adams smear campaigns in 1800. Or, you know, the Civil War, when the US literally split into two countries and we started killing each other en masse.
Thanks! Makes sense. (To be clear, I wasn’t saying that tight control by a single political faction would be a good thing… only that it would fix the polarization problem.) I think the Civil War era was probably more polarized than today, but that’s not very comforting given what happened then. Ideally we’d be able to point to an era with greater-than-today polarization that didn’t lead to mass bloodshed. I don’t know much about the Jefferson-Adams thing but I’d be surprised if it was as bad as today.