A psychologist, neuroscientist and philosopher got together to debate the meaning of free will. They walked onto the auditorium stage, sat down before an eager audience, and all crossed their left legs over their right.

The psychologist pointed out the similarity and asked if crossing their legs like so was a consequence of free will or a predetermined action.

This isn't the start of a long, bad joke.

At the World Science Festival, these three academics debated the age-old questions about the existence, meaning and moral consequences of free will in light of emerging knowledge of how the brain works. Paul Nurse, a Nobel laureate and president of Rockefeller University, moderated the debate on Saturday night among Daniel Wegner, a Harvard psychologist; Patrick Haggard, a neuroscientist at University College of London, and Alfred Mele, a philosopher at Florida State University.

People want to feel authorship of their actions, and so we make up stories about free will to explain them, said Dr. Wegner, who studies how people control and perceive their minds. The Harvard psychologist believes free will is the feeling that we somehow control the link between our thoughts and actions, though we can only guess about the actual causal pathway.

Intention and will are important parts of the mental process, but they can be explained biologically, Dr. Haggard said. The London neuroscientist studies the relationships between brain activity and subjective experience, particularly on how and when people become conscious of their intentions and actions.

"As a neuroscientist, you have to believe that conscious experiences are a result of brain activity," Dr. Haggard said.

Dr. Haggard defines free will as the ability to make decisions in complex situations in which there is no obvious choice. Through his research, he wants to learn more about how the brain does that.

Not being familiar with Dr. Mele's work, I was somewhat surprised that the philosopher agreed with Dr. Haggard that free will has biological roots. In fact, that is something all the men seemed to agree on: that free will is not a spiritual or magical experience endowed supernaturally within us, but rather, that the conscious decision-making ability is a result of organic brain activity.

That doesn't absolve one from more responsibility for their actions, said Dr. Mele, who has written several books on free will and its moral implications.

He prefers the term free action over free will to describe the control people have over what they do. Actions are a consequence of brain activity, which is based on millions of years of evolution and our own experiences. When we choose to act in absence of compulsion or a psychological disorder, then the conditions are sufficient for calling it free will and for ascribing moral responsibility, Dr. Mele said.

Physical actions like crossing one's legs hardly induce discussions of moral consequence. As scientists learn more about the brain's role in intention and action, though, Dr. Haggard said neuroscientists and lawyers may cross paths more frequently in societal debates over ethics, crime and punishment.

Dennis Overbye tackled these questions about free will in the Times a couple of years ago, when he wanted desperately to keep his New Year's resolution to fend off cravings for desserts. Was his decision to order the chocolate cake free will or predetermined by the laws of nature?

Mr. Overbye didn't seem to reach a clear conclusion, just as the experts' varying viewpoints Saturday night didn't leave the audience with many concrete answers. There seemed lots of room for competing viewpoints - assuming, of course, that we're all really free to disagree.