Dinner with a philosopher is never just dinner, even when it’s at an obscure Indian restaurant on a quiet side street in Princeton with a 30-year-old postdoctoral researcher. Joshua Greene is a man who spends his days thinking about right and wrong and how we separate the two. He has a particular fondness for moral paradoxes, which he collects the way some people collect snow globes.
“Let’s say you’re walking by a pond and there’s a drowning baby, ” Greene says, over chicken tikka masala. “If you said, ‘I’ve just paid $200 for these shoes and the water would ruin them, so I won’t save the baby,’ you’d be an awful, horrible person. But there are millions of children around the world in the same situation, where just a little money for medicine or food could save their lives. And yet we don’t consider ourselves monsters for having this dinner rather than giving the money to Oxfam. Why is that?”
Philosophers pose this sort of puzzle over dinner every day. What’s unusual here is what Greene does next to sort out the conundrum. He leaves the restaurant, walks down Nassau Street to the building that houses Princeton University’s psychology department, and says hello to graduate student volunteer Nishant Patel. (Greene’s volunteers take part in his study anonymously; Patel is not his real name.) They walk downstairs to the basement, where Patel dumps his keys and wallet and shoes in a basket. Greene waves an airport metal-detector paddle up and down Patel’s legs, then guides him i...