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 into an adjoining room dominated by a magnetic resonance imaging scanner. The student lies down on a slab, and Greene closes a cagelike device over his head. Pressing a button, Greene maneuvers Patel’s head into a massive doughnut-shaped magnet.
Greene goes back to the control room to calibrate the MRI, then begins to send Patel messages. They are beamed into the scanner by a video projector and bounce off a mirror just above Patel’s nose. Among the messages that Greene sends is the following dilemma, cribbed from the final episode of the TV series M*A*S*H: A group of villagers is hiding in a basement while enemy soldiers search the rooms above. Suddenly, a baby among them starts to cry. The villagers know that if the soldiers hear it they will come in and kill everyone. “Is it appropriate,” the message reads, “for you to smother your child in order to save yourself and the other villagers?”
As Patel ponders this question—and others like it—the MRI scans his brain, revealing crackling clusters of neurons. Over the past four years, Greene has scanned dozens of people making these kinds of moral judgments. What he has found can be unsettling. Most of us would like to believe that when we say something is right or wrong, we are using our powers of reason alone. But Greene argues that our emotions also play a powerful role in our moral judgments, triggering instinctive responses that are the product of millions of years of evolution. “A lot of our deeply felt moral convictions may be quirks of our evolutionary history,” he says.
