To look at the difference in approach that psychology and philosophy bring to the table, it might be useful to look at their perspectives on the same problem. Happily, there is a problem that has caught the imagination of both psychologists and philosophers: the so-called trolley problem—or, more accurately, trolley problems. Often in the academic literature, two runaway trolley scenarios are compared to each other. There are several variations on each of the scenarios, but basically they fall into two main types:
Scenario I: A runaway trolley will run over five people standing on the track unless you, a bystander, pull a switch and send the trolley onto a siding, where, unfortunately, there is one person who will be run over. Should you pull the switch?
Scenario II: You are standing on an overpass over the trolley track. The runaway trolley will run over five people further down the track unless you push a fat man off the bridge, allowing the trolley to hit and kill the man but stopping the trolley before it hits the five. Should you push the fat man?
The questions the psychologists ask and the questions the philosophers ask about these scenarios are very different. First, the psychologists want to know the answer to an empirical question: how do people generally answer the questions posed by the scenarios? (Answer: most people think it’s okay to pull the switch but not okay to throw the fat man.) They also want to know why people said they answered differently in the two cases. (Answer: most people couldn’t come up with a “reason”; the two scenarios just “felt different.”)
Next, the psychologists want to know why the scenarios felt different. (One empirical answer: according to functional MRI studies, people are more emotionally affected by the second scenario.)
Then psychologists want to know why people are more emotionally affected by the second scenario. (One answer: empathy for the fat man on the bridge is stronger than that for the person on the siding, because being the fat man on the bridge is more closely related to realistic, everyday fears of being harmed by strangers.)
Then psychologists want to know why the fear of being the fat man on the bridge would necessarily translate into empathy for the actual fat man. (One answer from evolutionary psychology: natural selection favored the survival of societies made up of people with an empathetic response to the prospect of killing each other.)
The interests of the philosophers intertwine in interesting ways with each of these psychologists’ questions.
First of all, at one level, the philosophers couldn’t care less about how actual people answered the questions posed by the two scenarios. The philosophers want to know how we should respond to the scenarios, and it is not out of the question for them that most people might have simply got it wrong. On the other hand, of course, it would be a very egotistical philosopher indeed who did not at least pause to ask herself if overwhelming popular support for an answer she did not share might be an indicator that she was the one who got it wrong. In any case, the philosopher sees the scenarios as posing ethical rather than factual questions. This difference accounts for the philosopher’s relative lack of interest in all of the other empirical questions the psychologist asks, questions about brain chemistry and MRI results and evolutionary development.
There are some psychologists, and some philosophers as well, who think that ethical questions are reducible to questions of psychological or evolutionary fact. They would say that the question, “Why should I not throw the fat man off the bridge?” is just another way of asking, “What psychological or neurological forces will determine whether or not I do, in fact, throw the fat man off?”
Next up, I want to take a look at what philosophers call the naturalistic fallacy and what it has to say about psychological determinism. And, finally, there are some specific concerns about evolutionary psychology that are posed by the philosophical discipline of epistemology.