“You sound to me as though you don’t believe in free will,” said Billy Pilgrim.

“If I hadn’t spent so much time studying Earthlings,” said the Tralfamadorian, “I wouldn’t have any idea what was meant by free will. I’ve visited thirty-one inhabited planets in the universe, and I have studied reports on one hundred more. Only on Earth is there any talk of free will.”

—From Slaughterhouse-Five, by Kurt Vonnegut

Imagine for a moment that instead of Timothy McVeigh destroying the Murrah Federal Building in Oklahoma City, it had been a mouse. Suppose this mouse got into the wiring of the electrical system, tangled the circuits and caused a big fire, killing all those inside. Now think of the victims’ families. There would, of course, still be enormous grief and suffering, but there would be one significant difference: There would no resentment, no consuming anger, no hatred, no need to see the perpetrator punished (even if the mouse somehow got out of the building) in order to experience “closure.” Why the difference? Because McVeigh, we think, committed this terrible act out of his own free will. He chose to do it, and he could have chosen not to. McVeigh, then, is morally responsible for the death of the victims in a way that the mouse would not be. And our sense of justice demands that he pay for this crime.

There is an undeniable human tendency to see ourselves as free and morally responsible beings. But there’s a problem. We also believe—most of us anyhow—that our environment and our heredity entirely shape our characters (what else could?). But we aren’t responsible for our environment, and we aren’t responsible for our heredity. So we aren’t responsible for our characters. But then how can we be responsible for acts that arise from our characters?

There’s a simple but extremely unpopular answer to this question: We aren’t. We are not and cannot be ultimately responsible for our behavior. According to this argument, while it may be of great pragmatic value to hold people responsible for their actions, and to employ systems of reward and punishment, no one is really deserving of blame or praise for anything. This answer has been around for more than two thousand years; it is backed by solid arguments with premises that are consistent with how most of us view the world. Yet few today give this position the serious consideration it deserves. The view that free will is a fiction is called counterintuitive, absurd, pessimistic, pernicious and, most commonly, “unacceptable,” even by those who recognize the force of the arguments behind it. Philosophers who reject God, an immaterial soul, and even...