It’s an interesting thought experiment, but it’s also a relevant one. Last spring, two news stories collided to create a culture-wide seminar in identity studies: Caitlyn Jenner, the former Olympic athlete, came out as transgender on the cover of Vanity Fair, and it was revealed that Rachel Dolezal, the former head of the Spokane chapter of the National Association for the Advancement of Colored People, had lied about her African American descent, although she has said she identifies as black. The two women’s stories are neither perfect analogs nor good representations of the experiences of other people who cross gender or racial lines, Brubaker writes. But the convergence of their experiences did offer an opportunity to explore and compare two unsettled forms of identity.

Many words have already been written about the Dolezal vs. Jenner debate—some thought-provoking essays are here, here, and here. The value in Brubaker’s book is not in readjudicating old internet battles, but in laying out current conflicts of identity in a public, accessible way; academics have been thinking and talking about the fluidity and fixedness of gender and race for a long time, but their thinking hasn’t always been part of mainstream conversations. Especially with the growing number of legislative, judicial, and cultural challenges to the role of gender in American society, sometimes, it can just be useful to lay out the terms of debate.

Brubaker and I spoke about the complexity of trans identity, largely in the context of gender, but also in the context of race. Our conversation has been edited and condensed for clarity.

Emma Green: What sets race and sex or gender apart as forms of identity?

Rogers Brubaker: They are similarly becoming massively unsettled. And yet, as you suggest, they are indeed very different.

There are two ways to think about that. The sex vs. gender distinction allows us to distinguish the inner gender identity from the outward sexed body. There’s no analogous way of separating out the inner from the outer in the domain of race. The inner gender identity can be understood as an essence that only the person concerned can know, and can be independent of the sexed body. We just can’t think about race in that way. It is incomprehensible if I tell you that I simply feel black.

Also, when we talk about race, ancestry matters. Ancestry doesn’t matter at all for sex or gender identity. Even though sex is in fact inherited, it is inherited in this way that has nothing to do with history or lineage or family or relationships. This permits us to think about gender as something that only the individual has the authority to determine, whereas others always have a stake in saying what someone’s racial identity is.

Green: This also seems to be a matter of a fundamental difference in worldview: the idea that individuals determine their identities, versus the belief that our identities are determined by nature, or a Creator, as some Christians might believe.