Few topics in recent years have gripped scholarly—and popular—attention the way the debate over polarization in the American public has. These two books take up different dimensions of that broad topic, asking different questions and arriving at different answers, but both help us to better understand this important aspect of our contemporary politics.

Morgan Marietta and David Barker study “dueling factual perceptions (DFPs),” which are “the degree to which people perceive facts differently” (p. 9). DFPs reflect the disagreement among Americans on topics such as anthropogenic climate change, the role of racism in the United States, and whether homosexuality is innate. These authors argue that DFPs represent an important form of polarization: disagreement not about the best public policies (issue polarization) but about the underlying facts of the matter. DFPs, they argue, are a result of not only partisan opinion leadership but also divergent values. These competing values reflect distinct epistemologies—meaning that DFPs cannot be resolved simply by providing people with more (or better) information. We cannot educate our way out of the problem. DFPs stem from the two sides having fundamentally different worldviews.

This book does an admirable job of exploring these DFPs, highlighting their complex etiologies and—depressingly—documenting how difficult they will be to resolve. The reader will leave the book having been convinced that DFPs pose a pernicious problem: the two sides believe different things not just because they follow different partisan cues, but because they hold quite different sets of core values (a conclusion with a clear parallel to Jonathan Haidt’s arguments about the parties’ different moral foundations in his 2012 book, The Righteous Mind). Furthermore, the material in chapter 12—discussing the striking partisan polarization in views of higher education—should give all academics pause. A fascinating topic for future work will be exploring whether distrust in the academy correlates with support for leaders such as former President Trump who routinely question expert judgments.

Despite these strengths, after reading the book, there were two areas where I wanted it to do more. First, the book could have more fully engaged with the possibility that expressive responding may explain some DFPs (Brian Schaffner and Samantha Luks, “Misinformation or Expressive Responding? What an Inauguration Crowd Can Tell Us about the Source of Political Misinformation in Surveys,” Public Opinion Quarterly, 2018). This type of survey response partially—although not fully—explains this sort of divergence elsewhere (John Bullock, Alan Gerber, Seth J. Hill, and Gregory Huber, “Partisan Bias in Factual Beliefs about Politics,” Quarterly Journal of Political Science, 2015; Omer Yair and Gregory Huber, “How Robust Is Evidence of Partisan Perceptual Bias in Survey Responses? A New Approach for Studying Expressive Responding,” Public Opinion Quarterly, 2020), so it would be fascinating to unpack how it shapes DFPs (if at all).

Second, I have lingering concerns about the extent to which the analysis can fully disentangle the effects of values from the effects of partisanship. As the authors note, these factors are deeply interconnected, and to address this, they “fully account for partisan and other identities, in our attempt to clarify the independent role of values as DFP motivators” (p. 109, footnote 8). This is a sensible approach, but the problem is likely intractable. Values are endogenous to partisanship (Paul Goren, “Party Identification and Core Political Values,” American Journal of Political Science, 2005; Annemarie Walter and David Redlawsk, “Voters’ Partisan Responses to Politicians’ Immoral Behavior,” Political Psychology, 2019), and values drive political behavior because partisan political elites invoke those values in their rhetoric (Paul Goren, Christopher Federico, and Miki Caul Kittilson, “Source Cues, Partisan Identities, and Political Value Expression,” American Journal of Political Science, 2009). Because few voters, except perhaps the most sophisticated, would be able to map values into political beliefs without party cues, to what extent can we meaningfully discuss their independent effects conceptually or empirically? This cannot be solved by simply controlling for various factors in a regression or running an experiment in which one primes a particular factor. An important topic for future work, then, will be to think of research designs that allow scholars to more fully disentangle these two competing explanatory factors.

Stacy Ulbig takes up a different dimension of our polarized political moment by focusing on affective polarization—or the extent to which individuals do not just disagree on facts or issues, but instead actively dislike one another. She studies this in a distinctive population: college students, which makes good sense given that today’s students will be tomorrow’s voters and leaders. Although we know a lot about this population’s psychological tendencies (thanks to several generations of lab studies in psychology), we know much less about their partisan attitudes, which are still changing and adapting as they begin to become politically active. Ulbig’s data suggest that college students, like the public more generally, have a large degree of animosity toward the other party.

The focus on college students is novel and welcome, and scholars of partisan animus will find many fascinating results in these analyses. The book makes an important contribution in arguing that partisan animosity has multiple dimensions (organizational vs. interpersonal vs. physical; see below) and in highlighting that they might have different causes and different effects. This innovation will undoubtedly inspire future scholarship to refine and extend these ideas. The book will also be an excellent teaching tool—students will enjoy reading about their peers and comparing their own degree of partisan animosity to the levels seen in the book.

That said, there are two areas where more scholarship will be needed to fully integrate these findings into the literature. First, Ulbig draws on a novel set of items to measure affective polarization, which are taken from the literature on ethnic antagonism (Eran Halperin, Daphna Canetti, and Shaul Kimhi, “In Love with Hatred: Rethinking the Role Hatred Plays in Shaping Political Behavior,” Journal of Applied Social Psychology, 2012). Factor analysis suggests that there are three main dimensions to this animosity: physical hatred (wanting to harm those from the other party), organizational hatred (anger at the other party’s leaders and dislike of their policies), and interpersonal hatred (an unwillingness to spend time around members of the other party; there is also a fourth dimension of national hatred, but this is uncorrelated from the others, so it gets dropped from the analyses, see Table 3.5 on pp. 70–71 and Table 3.6 on p. 73).

Although such a novel measure is admirable, it is not always clear how it maps back to other findings in the literature. For example, in chapter 4, we see that partisan and ideological strength, as well as media consumption, have different—sometimes quite different—correlations with these various dimensions, suggesting that they have different origins, and might map quite differently in other manifestations of partisan animosity (such as trust in the other party, or trait ratings of them, or discrimination against them). This new measure is an important innovation, but we need to know more about how it relates to earlier work to understand its place in the literature.

Second, the results in this book suggest that these different dimensions of partisan animosity have different causes, and also different effects, especially with respect to outcomes such as political compromise. More theorizing will be needed to build an understanding of why and how these dimensions of animosity generate pernicious outcomes and—fascinatingly—why they seem to diverge so much by party. It is particularly striking, as Ulbig argues, that organizational hatred (dislike of the other party and its policies) seems to be quite distinct from interpersonal hatred (dislike of other partisans), which suggests that different treatments may be needed to ameliorate these two dimensions of animus.

Both books end by noting—correctly—that there are no easy solutions to these problems; there is no “one weird trick” to fix our contemporary politics. The ultimate solutions will need to be elite driven, but that is effectively calling for a deus ex machina. In the interim, is there anything that can help? This is a critical area of research, and I would point to two slightly different pathways that could offer some amelioration, though not cessation, of these hostilities. First, in terms of partisan animosity, there are a number of active areas of research, but Ulbig highlights one area that deserves more attention: the idea that civil debate and dialogue is a skill that needs to be taught (see especially the discussion on pp. 188–92). One way to reduce interpersonal partisan animosity may be to help people understand how to dialogue across lines of difference. Such an effort recognizes that civics education should not simply ask students to memorize facts about our government, but should help them gain a broader understanding of how to be a citizen in a pluralistic democracy.

Second, the solution to DFPs is even trickier and more incomplete. As Marietta and Barker argue, the extant approaches—better education and more fact-checking—will not work because they do not address the underlying issue of different epistemologies. DFPs, as they note, “are here to stay” (p. 283). But I will end on a minor note of optimism. One potential pathway may be to delink values from actions so that divergent epistemologies are not activated (Dan Kahan, “Fixing the Communications Failure,” Nature, 2010). Rather than trying to force agreement that global warming is both real and caused by humans, we should focus on how to solve the problems at hand, such as rising sea levels and droughts. In effect, this calls for citizens to recognize that there is no “solution” to fundamentally different values, and attention is focused on local action to solve tractable problems. The authors might respond that this sidesteps the larger, more fundamental issue, to which I can only agree. But democratic self-governance does not guarantee agreement on issues of facts or values. Instead, it offers us a path toward solving problems via political contestation. No doubt both books will inspire scholars to push forward with research to understand how we can do just that.