February 21, 2016
The Data Against Kant
The history of moral philosophy is a history of disagreement, but on one point there has been virtual unanimity: It would be absurd to suggest that we should do what we couldn’t possibly do.
This principle — that “ought” implies “can,” that our moral obligations can’t exceed our abilities — played a central role in the work of Immanuel Kant and has been widely accepted since. Indeed, the idea seems self-evidently true, much as “bachelor” implies “man.”
But is it actually true? In 1984, the philosopher Walter Sinnott-Armstrong (above) outlined a series of thought experiments that, he contended, demonstrated that “ought” does not always imply “can.” Though his argument found some adherents, most philosophers were not convinced. We think that the consensus view that “ought” implies “can” is mistaken. In a psychological study to be published in the May issue of the journal Cognition, we offer empirical evidence suggesting that Professor Sinnott-Armstrong was right.
His thought experiments go something like this: Suppose that you and a friend are both up for the same job in another city. She interviewed last weekend, and your flight for the interview is this evening. Your car is in the shop, though, so your friend promises to drive you to the airport. But on the way, her car breaks down — the gas tank is leaking — so you miss your flight and don’t get the job.
Would it make any sense to tell your friend, stranded at the side of the road, that she ought to drive you to the airport? The answer seems to be an obvious no (after all, she can’t drive you), and most philosophers treat this as all the confirmation they need for the principle.
Suppose, however, that the situation is slightly different. What if your friend intentionally punctures her own gas tank to make sure that you miss the flight and she gets the job? In this case, it makes perfect sense to insist that your friend still has an obligation to drive you to the airport. In other words, we might indeed say that someone ought to do what she can’t — if we’re blaming her.
Three decades after Professor Sinnott-Armstrong made this argument, we decided to run his thought experiments as scientific ones. (We partnered with Professor Sinnott-Armstrong himself, along with the philosopher Felipe De Brigard.) In our study, we presented hundreds of participants with stories like the one above and asked them questions about obligation, ability and blame. Did they think someone should keep a promise she made but couldn’t keep? Was she even capable of keeping her promise? And how much was she to blame for what happened?
We found a consistent pattern, but not what most philosophers would expect. “Ought” judgments depended largely on concerns about blame, not ability. With stories like the one above, in which a friend intentionally sabotages you, 60 percent of our participants said that the obligation still held — your friend still ought to drive you to the airport. But with stories in which the inability to help was accidental, the obligation all but disappeared. Now, only 31 percent of our participants said your friend still ought to drive you.
Professor Sinnott-Armstrong’s unorthodox intuition turns out to be shared by hundreds of non-philosophers. So who is right? The vast majority of philosophers, or our participants?
One possibility is that our participants were wrong, perhaps because their urge to blame impaired the accuracy of their moral judgments. To test this possibility, we stacked the deck in the favor of philosophical orthodoxy: We had the participants look at cases in which the urge to assign blame would be lowest — that is, only the cases in which the car accidentally broke down. Even still, we found no relationship between “ought” and “can.” The only significant relationship was between “ought” and “blame.”
This finding has an important implication: Even when we say that someone has no obligation to keep a promise (as with your friend whose car accidentally breaks down), it seems we’re saying it not because she’s unable to do it, but because we don’t want to unfairly blame her for not keeping it. Again, concerns about blame, not about ability, dictate how we understand obligation.
So here we face the other possibility, one less flattering to most moral philosophers: It’s their moral judgments that are distorted.
While this one study alone doesn’t refute Kant, our research joins a recent salvo of experimental work targeting the principle that “ought” implies “can.” At the very least, philosophers can no longer treat this principle as obviously true.
In the last decade or so, the “experimental philosophy” movement has argued for greater use of empirical science to inform and shape the discussion of philosophical problems. We agree: Philosophers ought to pay more attention to their colleagues in the psychology department (even if they can’t).