Think of the discipline of philosophy, and a certain sort of image springs to mind. Perhaps you visualize a person sitting comfortably in an armchair, lost in thought, perusing a few old books. Maybe you imagine a field that is scholarly, abstruse by nature and untethered to any grounding in real science. At any rate, you probably do not think of people going out and running experiments.

Yet oddly enough, a cadre of young philosophers have begun doing just that. These “experimental philosophers” argue that inquiry into the most profound questions of philosophy can be informed by actual investigations into why people think and feel as they do. To make progress on these questions, they use all the methods of contemporary cognitive science. They conduct experiments, team up with psychologists and publish in journals that had previously been reserved primarily for scientists. The result has been something of a revolution. Although the movement began only a few years ago, it has already spawned hundreds of papers, a steady stream of surprising results and some very strong opinions on every side.

All of this might at first seem deeply peculiar—almost as though philosophers have stopped doing real philosophy and started switching over to something else entirely. Yet perhaps this approach isn’t actually quite as odd as it might initially appear. In a typical research program, scientists work with certain instruments (telescopes in astronomy, microscopes in biology, and so on). Usually they don’t think much about the instruments themselves; they simply use them to get at some independently existing reality. Still, now and then researchers get puzzled or confused by the information coming from their instruments. Maybe this information seems wildly implausible, or goes against established bodies of theory, or is internally contradictory. In such cases, it often proves helpful to turn away from the reality one is primarily trying to study and to look in detail at the instruments themselves. One might even find that the best way to resolve a question in astronomy is to start engaging in a scientific study of telescopes.

Now, philosophers do not make much use of telescopes or microscopes. We rely almost entirely on one particular instrument: the human mind, which produces the ideas that drive our profession. Still, the same basic principle applies. Typically we do not worry too much about the workings of our own minds and simply use them to get at an independent reality. Sometimes this approach fails, though. Sometimes our mind seems to pull us in two directions, almost as if two different voices within us are giving opposite answers to the same question. In situations like these, it can be helpful to explore the mind itself and to look scientifically at the sources of our own and others’ philosophical intuitions.

This is where experimental philosophy comes in. The key idea is that if we can get a better understanding of the psychology behind philosophical intuitions, we can have a better sense of which intuitions are worthy of our trust and which we should dismiss as unreliable or misleading.

This work, we hope, will give us a better understanding of people’s beliefs about the great philosophical issues. How is it that individuals come to believe in free will? Do they see their own moral claims as objective truths? The findings could ultimately have practical implications in jurisprudence, ethics and other fields.

Free Will, Experimental-Style
Imagine witnessing a murder. As you look at the scene in front of you, it may initially seem obvious that the murderer is morally responsible for what he has done and absolutely deserving of punishment. Now suppose you pause to think the matter over philosophically. The murderer’s action was presumably caused by certain mental states he had, and these mental states were probably caused by yet earlier events ... so that ultimately his act might just be the final step in a chain that could be traced back to certain facts about his genes and environment. Yet if that sequence shaped him, can he ever really be morally responsible for the things he has done? Some philosophers say yes, others say no, and the debate between these two positions has gone back and forth endlessly. This is the age-old problem of free will.

Experimental philosopher Shaun Nichols of the University of Arizona and I thought that the conflict surrounding this problem might have its roots in a tension between two forms of human cognition. Perhaps our capacity for abstract theoretical reflection leads us to think in one way, whereas our more immediate emotional responses pull us in exactly the opposite direction. One impulse tells us: “Well, if you think about it rationally, his behavior is just one step in a complex causal chain, and he can therefore never really be truly free or responsible.” Then another one intrudes: “Wait! This guy is a murderer! He simply has to be to blame for what he has done.”

In conducting an experiment, Nichols and I started out by asking participants about a fictitious universe (“Universe A”) in which everything anyone did was completely determined by a chain of causation stretching back into the past.

Each participant was then randomly assigned to one of two conditions. Those in one condition were asked a question designed to trigger abstract theoretical reflection:

In Universe A, is it possible for people to be fully morally responsible for their actions?

Participants in the other condition were given a highly concrete, even lurid story designed to elicit a more emotional response:

In Universe A, a man named Bill is attracted to his secretary and decides that the only way to be with her is to kill his wife and three children. He knows that it is impossible to escape from his house in the event of a fire. Before leaving on a business trip, he sets up a device that burns down the house and kills his family. Is Bill fully morally responsible for killing his wife and children?

Those who got the abstract the­oretical question tended to say no—no one can be morally responsible in a deterministic universe—whereas those who got the second, more concrete question tended to take exactly the opposite view, saying Bill did indeed bear responsibility for his actions. In other words, people claim in the abstract that no one can be morally responsible in a deterministic universe, but when they are confronted with a story about a specific individual engaged in some dastardly deed, they are perfectly willing to say he is morally responsible regardless of what kind of universe he happens to live in.

Although this first study was relatively small, conducted on a few dozen American undergraduates, the next few years saw a number of attempts to explore these phenomena more rigorously. One such experiment used a much larger sample (with more than 1,000 participants); another looked at intuitions about the abstract case across a number of different cultures (India, Hong Kong, Colombia and the U.S.). Each time the original findings continued to emerge. At that point, it did seem that we had latched onto some kind of genuine effect, yet questions remained about why exactly this effect was arising. Did the effect actually reflect a difference between abstract and concrete thinking? To further explore the issue, we needed studies that used somewhat different methods.

One of the most striking and elegant tests was conducted by experimental philosopher Christine Weigel of Utah Valley University. All participants were told to imagine hearing a philosophy lecture about the problem of free will. The lecture they were asked to imagine explained the problem in a general way and then concluded with the very example described earlier: a man in a deterministic universe who kills his own wife and children. But Weigel then introduced an incredibly subtle manipulation. Some participants were asked to imagine that the lecture was happening “in a few years,” whereas others were asked to imagine that the lecture was happening “in a few days.”

This manipulation might not seem to have anything much to do with free will, but it does have a lot to do with human cognition. A whole series of experimental studies have shown that imagining an event at a more distant time leads people to employ a different type of cognitive process: more abstract, theoretical and high level. In other words, the story about the more distant time should trigger a more reflective sort of process (“‘Well, if you think about it rationally....”), and the story about the closer time should trigger individuals’ more concrete intuitions (“Wait! This guy is a murderer!”). Sure enough, Weigel found that her manipulation was changing people’s intuitions. Those who were told to imagine a more distant event ended up being less likely to say that human beings could be morally responsible even in a deterministic universe.

It is beginning to seem increasingly plausible that people’s sense of perplexity and inner conflict regarding the problem of free will does indeed derive from a tension between their more abstract theoretical judgments and their more concrete emotional responses. Moreover, the situations they find themselves in at a given moment markedly influence the moral stances they adopt.

Of course, the mere fact that this hypothesis has received support in a few initial studies does not prove that it is true. Experimental philosopher Eddy Nahmias of Georgia State University has proposed an important rival hypothesis that does not involve any conflict between reason and emotion, and it is widely agreed that the evidence available now from these experiments is not sufficient to resolve all the major questions. At the very least, though, what we have here is definitely a start. Although a great deal still remains to be done, we now have the beginnings of an experimental research program on the psychological roots of people’s understanding of free will.

Is Morality Relative?
I have been focusing thus far on issues that may seem a little bit abstruse or academic, but experimental philosophy can also help illuminate the questions at the heart of contemporary controversies about morality.

Imagine that Sven and Xiex are from two different cultures. Sven says, “Hitting other people is morally bad,” whereas Xiex says, “Hitting other people is perfectly fine—just the right way to prove one’s strength and valor.” We now face a difficult question: Given that Sven and Xiex have opposite opinions, does one of them have to be wrong? Or could it be that there is no single right answer here, so that each of them can be right relative to his own culture’s system of values?

Of all the complex theoretical questions discussed by philosophers, this one has been among the most polarizing within Western culture as a whole. Campus radicals of various stripes often suggest that there is no single moral truth and that morality is always fundamentally relative; more conservative thinkers often insist on the existence of objective moral truths. Pope Benedict XVI himself recently waded into the debate, declaring that moral relativism leads “to moral or intellectual confusion, to a lowering of standards, to a loss of self-respect, and even to despair.”

In an attempt to get at the psychological roots of this controversy, psychologist Edward T. Cokely of Michigan Technological University and philosopher Adam Feltz of Schreiner University gave study participants a story about people who hold opposite views on a moral question. Subjects were then asked whether one disputant had to be wrong (the antirelativist answer) or whether there might be no single correct position (the relativist answer). Cokely and Feltz’s study also included an interesting twist.

They gave each participant a standard measure of the personality trait “openness to experience,” and they were able to determine which participants were more open to experience and which were more closed. The results showed a significant correlation: the higher a participant was in openness to experience, the more likely that participant was to endorse the relativist answer.

These studies suggest a hypothesis about the roots of relativism. Perhaps the pull people sometimes feel toward moral relativism is related to a kind of openness. When confronted with other perspectives and other possible ways of life, they feel drawn to relativism to the extent that they open themselves up to these other possibilities and enter into them imaginatively.

In an innovative test of this hypothesis, psychologists Geoffrey Goodwin of the University of Pennsylvania and John Darley of Princeton University measured participants’ ways of thinking by giving each of them a logic puzzle that involved configuring blocks in a certain way. Although the problem seemed straightforward on the surface, there was actually a trick: one could only get the right answer by looking at the problem from multiple perspectives. The key research question then was about the relation between people’s abilities in solving this problem and their intuitions about relativism. Surprisingly enough, the researchers again found a significant correlation. Those who got the problem right were especially likely to offer relativist answers.

Thus, we are beginning to see a kind of convergence. We have a series of different studies, conducted by different researchers, using quite different methods, and yet they all seem to be pointing toward the same basic conclusion: people feel drawn to relativism to the extent that they can open themselves to other possible perspectives. This result may help give us some much needed insight into the roots of one of the most enduring philosophical controversies of our time.

Should We Burn the Armchair?
Suppose now, if only for the sake of argument, that experimental philosophy continues to make progress. Imagine that all our empirical questions are resolved and that we eventually arrive at an accurate understanding of the cognitive processes underlying people’s philosophical views. Even then, it may seem that we would not have fully addressed the original question at the heart of the philosophical debate—namely, whether these views are actually right or wrong. This latter question, one might think, just isn’t even the sort of thing one could potentially answer by doing experiments. Sooner or later someone is going to have to get back into that armchair and reflect hard on the philosophical issues themselves.

Taken in itself, this point is eminently fair and reasonable, and any philosopher should be happy to accept it. But it would be a big mistake to treat it as some devastating objection to the whole project of experimental philosophy. No one is suggesting that philosophers should abandon other forms of thought and spend their time running experiments; rather experimental work should be part of a larger philosophical inquiry. Experimental philosophy is just adding a tool to the philosopher’s toolbox. As we are sitting in our armchairs wrestling through the tensions among our different beliefs, it can sometimes be helpful, and occasionally indispensable, to have a better understanding of the cognitive processes that gave rise to those beliefs.

This article was originally published as "Thought Experiments."