The idea of human nature is riven with controversy. Some scholars—often those in the humanities—argue that there’s no such thing, while others—often those in the social and biological sciences—regard its “denial” as anti-scientific. So is there any point hanging onto this controversial idea?

The Great Chain of Being—the notion that the biosphere is partitioned into ranks, with humans at the top, and every other organism at some inferior position—is a way of thinking that’s incredibly difficult, if not impossible, to dislodge. Most of us have a strong conviction that it’s true, but we don’t have a clue why we think that.

The Rachel Divide, a documentary about Rachel Dolezal and the controversy over her claims to racial identity, came out in April on Netflix. The movie would have benefited, however, from some philosophical consideration of what race is—or is not—and what claims to racial identity assert.

Are we alone in the universe? Or is the cosmos teeming with life? And what difference would it make if we found the answer? Those are just some of the questions we address in this week's show.

Most philosophical work on race concentrates on two questions. The first is the question of whether race is real. Are there really kinds of people corresponding to racial categories like “white” and “black,” or is this merely an illusion? Suppose that races are real.