My primary research aim has been developing New Diversity Theory, a novel approach to social and political philosophy that I first began developing in my 2016 book Social Contract Theory for a Diverse World. Older approaches view diversity as simply a problem to be managed, and theorists either abstract it away, or argue that ideally we will come to agree on questions of justice. New Diversity Theory views diversity as resource to be leveraged by liberal societies. The core building block of this approach is a perspective – a way of categorizing the natural and social world. Part of our diversity is our diversity of perspectives. Using perspectives, we can see that our normative disputes are often not just about evaluative disagreements but may hinge on how we see the world. In one sense this makes our disagreements even deeper. But it also creates space for learning and reconciliation. A diverse populace will feature more disagreement, but it contains within it greater resources for social discovery and moral improvement.

New Diversity Theory is a variety of non-ideal theory. In ideal theory, theorists imagine agents who are perfectly motivated to follow the dictates of justice, and act as ideal rational agents in doing so. In non-ideal theory, we suppose people like us: people with epistemic limitations, a plurality of motivations, who may substantively disagree about what justice consists in, but nevertheless see a value in finding a way to coordinate with others and hold each other to account. I have argued for a greater embrace of experiments in living, and a more epistemically humble approach to theorizing about just social arrangements. In more recent work, I have argued that liberal theories of justice cannot rest on equilibrium conceptions of justice, because the exercise of liberal rights is disequilibriating. Shifting toward a model of liberalism as a process of experimentation and exploration of a changing landscape better captures what’s distinctive about liberalism compared to its more authoritarian alternatives. Central to this idea is that there is no “final” or “ideal” liberal account of justice or institutions that embody it. Instead, we should explore how to facilitate social learning among equals, so our institutions can change through time in a manner consistent with maintaining our capacity for future learning.

I have also fostered several smaller projects. The biggest of these projects is my work on social norms, and its intersection with political philosophy and policy. I co-authored the Stanford Encyclopedia of Philosophy entry on Social Norms, and I wrote the Social Norms chapter for the Routledge Handbook on Philosophy, Politics and Economics. I co-wrote two papers exploring the dynamics of norm emergence (2014a, 2014b). I co-wrote an experimental paper that demonstrates that trusting behaviors are not social norms, but trustworthy behaviors are (2011). More recently, I have been working on extending Bicchieri’s theory to give me better purchase on problems at the intersection of social and political philosophy. I’ve argued that perspectives shape what agents take to be evidence, and so countervailing evidence against a current norm may be “invisible” to the agents who would need it to change behavior (2017, 2018). I’ve also considered the extent to which social norms should be seen as a less-coercive alternative to the exercise of state power (2020, 2022). I argue that norms can be more deeply coercive, and lack anything like Hart’s secondary rules, and so their coercion can often be less just than state action via a legal system (2018).

Another ongoing project has been developing a framework for free speech in deeply diverse societies. Mill and many free speech advocates tend to have a background assumption that the participants in the speech environment are fixed. I have argued that they are endogenous to speech practices: we can induce people to enter or exit based on the burdens our speech norms create (2017, 2018). I have also argued most recently that large, diverse populations have unique challenges for establishing a healthy speech environment because of the limits of attention. This scarcity means that generalist speech venues will limit minority views. But more while more specialized speech venues facilitate more kinds of speech, they also create the conditions for polarization (2022).

As part of my broader interests in Philosophy, Politics and Economics, I study social dynamics that shape our interactions with each other at the local level. In work with Hankins and Schaefer, I have revisited the Hong-Page model of group learning. We show that once miscommunication is present, whether homogenous groups or diverse groups perform better is a function of institutions – the way their joint search task is structured. We believe this is the first step in a broader exploration of diversity and institutional structure (2023).

I have written on how people come to discover the social rules around them. Most recently, in joint work with Nichols and Sytsma, I have argued that what rules we coordinate on is crucially dependent on our second-order beliefs about universality. Universality beliefs can facilitate coordination, but they can over-facilitate coordination into domains where the coordination is unfair, like gendered divisions of labor, or unnecessary, like where we can simply have different matters of taste (2021). I’ve also written on segregation dynamics. My first paper (2011) demonstrated that even when people favor living in more diverse neighborhoods, they can still end up segregated. Most recently, I’ve argued that Schelling-style segregation models can be enriched with a more philosophically sophisticated model of social identity. I explore three different approaches to social identity that relate to important strands in liberal theory, and show how, with this more robust account, we can generate stable integration. Importantly, this does not assume we achieve integration by imagining nicer people, but we do so through increasing social diversity (2023). Relatedly, I have been interested in the ways in which associations, neighborhoods, and clubs can reshape civic relations. I argue that polycentric orders, while important tools for a diverse society, have tradeoffs that are under-appreciated, including imposing costs on those who are not party to the association. This generates challenges for political accountability (2021). I expect to continue to pursue this, both as a modeling project in exploring the dynamics of clubs and associations, and a more nuanced account issues of local justice.