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DANIEL DENNETT: For billions of years on this planet there was life, but no free will. Physics hasn't changed, but now we have free will. The difference is not in physics. It has to do with, ultimately, with biology. Particularly evolutionary biology. What has happened over those billions of years, is that greater and greater competences have been designed and have evolved. And the competence of a dolphin, or of a chimpanzee, the cognitive competence, the sort of mental competence, is hugely superior to the competence of a lobster, or a starfish. But ours dwarfs the competence of a dolphin or a chimpanzee, perhaps to an even greater extent. And there's an entirely naturalistic story to say, to tell about how we came to have that competence, or those competences. And it's that, "Can do." It's that power that we have which is natural, but it's that power which sets us aside from every other species. And the key to it is that we don't just act for reasons. We represent our reasons to ourselves and to others. The business of asking somebody, "Why did you do that?" And the person being able to answer, it is the key to responsibility. And in fact, the word, "responsibility," sort of wears its meaning on its sleeve. We are responsible because we can respond to challenges to our reasons. Why? Because we don't just act for reasons, we act for reasons that we consciously represent to ourselves. And this is what gives us the power and the obligation to think ahead, to anticipate, to see the consequences of our action. To be able to evaluate those consequences in the light of what other people tell us. To share our wisdom with each other. No other species can do anything like it. And it's because we can share our wisdom that we have a special responsibility.

That's what makes us free in a way that no bird is free, for instance. There's a very sharp limit to the depth that we as conscious agents can probe our own activities. This sort of superficial access that we have to what's going on, that's what consciousness is. Now, when I say, who's this, "we," who's got this access? That's itself part of the illusion because there isn't a, sort of, boss part of the brain that's sitting there with this limited access. That itself is part of the illusion. What it is, is a bunch of different subsystems, which have varying access to varying things and that conspire in a sort of competitive way to execute whatever projects it is that they're, in their, sort of, mindless way executing.

STEVEN PINKER: I don't believe there's such a thing as free will in the sense of a ghost in the machine, a spirit, or soul that somehow reads the TV screen of the senses and pushes buttons and pulls levers of behavior. There's no sense that we can make of that. I think we are...our behavior is the product of physical processes in the brain. On the other hand, when you have a brain that consists of a hundred billion neurons, connected by a hundred trillion synapses, there is a vast amount of complexity. That means that human choices will not be predictable in any simple way from the stimuli that have impinged on it beforehand. We also know that that brain is set up so that there are at least two kinds of behavior. There's what happens when I shine a light in your eye and your iris contracts, or I hit your knee with a hammer and your leg jerks upward. We also know that there's a part of the brain that does things like choose what to have for dinner, whether to order chocolate, or vanilla ice cream. How to move the next chess piece. Whether to pick up the paper, or put it down. That is very different from your iris closing when I shine a light in your eye. It's that second kind of behavior, one that engages vast amounts of the brain, particularly the frontal lobes, that incorporates an enormous amount of information in the causation of the behavior, that has some mental model of the world, that can predict the consequences of possible behavior and select them on the basis of those consequences. All of those things carve out the realm of behavior that we call free will. Which it is useful to distinguish from brute involuntary reflexes, but which doesn't necessarily have to involve some mysterious soul.

ROBERT SAPOLSKY: The polite thing that I've sort of said for decades, is that, well, if there's free will, it's in all the boring places and those places were getting more and more cramped. If you want to insist that today you decided to floss your teeth starting on your upper teeth, rather than your lower teeth, rather than the other way around, that that was an act of free will, whatever, I'll grant that one to you, that's where the free will is. In reality, I don't think there's any free will at all. If you look at the things that come into account as to whether or not someone is going to do the right thing in the next two seconds amid a temptation to do otherwise, and the variables in there reflect everything from whether they are having gas pains that day, because of something unpleasant they ate that morning that makes us more selfish, more impulsive, et cetera, to what epigenetic effects occurred to them than when they were a first trimester fetus. When you look at the number of things we recognize now that are biological organic, where 500 years ago, or five years ago, we would have had a harsh moral judgment about it. And instead we now know, "Oh, that's a biological phenomenon." And when we're we gonna get to the point is recognizing, "Yeah, we're biological organisms." This notion of free will, for want of a less provocative word, is nothing but a myth.

BILL NYE: Our brains are complicated and they got this big, or as big as they are organically through evolution, with layer being added upon layer. So our ability to choose is often confused. Our ability to make choices and is often affected by the environment, by our experiences and by biochemistry. The shape of our brain.

MICHIO KAKU: Well, you ask one of the deepest philosophical questions of physics. The question of free will. First of all, there's something called, Newtonian determinism. Newtonian determinism says that the universe is a clock. A gigantic clock that's wound up at the beginning of time and it's been ticking ever since, according to Newton's laws of motion. So, what you're gonna eat 10 years from now on January 1st has already been fixed. It's already known using Newton's laws of motion. Einstein believed in that. Einstein was a determinist. And some people asked Einstein, "Well, does that mean "that a murderer, a horrible mass murderer "isn't really guilty of his works "'cause it was already preordained billions of years ago?" And Einstein said, "Well, yeah, in some sense, that's true. "That even mass murderers were predetermined. "But," he said, "They should still be placed in jail," okay? Heisenberg then comes along and proposes the Heisenberg uncertainty principle. And says, "Nonsense. "There's uncertainty. "You don't know where the electron is. "It could be here, here, or many places simultaneously." And this of course, Einstein hated because he said, "God doesn't play dice with the universe." Well, hey, get used to it. Einstein was wrong. God does play dice. Every time we look at an electron, it moves. There's uncertainty with regards to the position of the electron. So what does that mean for free will? It means, in some sense, we do have some kind of free will. In the sense that no one can determine your future events given your past history. There's always the wild card. There's always the possibility of uncertainty in whatever we do. So this means that free will, determining the future? Hey, these are philosophical questions that seem to indicate that we have some kind of free will.

JOSCHA BACH: Like consciousness, free will is often misunderstood because we know it by reference. But it's difficult to know it by content, what you really mean by free will. A lot of people will immediately feel that free will is related to whether the universe is deterministic, or probabilistic. And while physics has some ideas about that, which change every now and then, it's not part of our experience. And I don't think it makes a difference if the universe forces you randomly to do things, or deterministically. The important thing seems to me that in free will you are responsible for your actions. And responsibility is a social interface. For instance, if I am told that if I do X I go to prison and this changes my decision to whether or not to do X, I'm obviously responsible for my decision because it was an appeal to my responsibility, in some sense. Or likewise, if I do a certain thing that it causes harm to other people and I don't want that harm to happen, that influences my decision. This is a discourse of decision-making that I would call it's a free will decision. Will is the representation that my nervous system, at any level of its functioning, has raised a motive to an intention. It has committed to a particular kind of goal and it gets integrated into the story of myself. This protocol that I experience as myself in this world. And that was what I experienced as well, as a real decision. And this decision is free in as much as this decision can be influenced by discourse.

MICHAEL GAZZANIGA: The essential part of free will that people wanna hold on to is the sense that that therefore makes you responsible for your actions. So, there is the idea of personal responsibility. And I think that's very important. And I don't think that all this mechanistic work on the brain in any way threatens that. You learn that responsibility is to be understood at the social level. The deal, the rules that we work out, living together. So the metaphor I like to use is cars and traffic. We can study cars and all their physical relationships and know exactly how that works. It in no way prepares us to understand traffic when they all get together and start interacting. That's another level of organization and description of these elements interacting. So the same is with brains. That we can understand brains to the nth degree and that's fine and that's what we're doing, but it's not going to, in any way, interfere with the fact that taking responsibility in a social network is done at that level. So, the way I sum it up is that brains are automatic, but people are free because people are gonna be...are joining the social group and in that group are laws to live by. And it's interesting, every social network, whether it's artifactual, internet, or people, that accountability is essential, or the whole thing just falls apart.

DENNETT: Intuition pumps are sometimes called thought experiments. More often, they're called thought experiments. But they're not really formal arguments. Typically, they're stories. They're little fables. In fact, I think they're similar to Aesop's fables in that they they're supposed to have a moral. They're supposed to teach us something. And what they do, is they lead the audience to an intuition, a conclusion, where you sort of pound your fist on the table and you say, "Oh yeah, it's gotta be that way, doesn't it?" And if it achieves that, then it's pumped the intuition that was designed to pump. These are persuasion machines. They're little persuasion machines that philosophers have been using for several thousand years.

One of my recent favorites, which I devised to jangle the nerves of neuroscientists who've been going around saying that neuroscience shows that we don't have free will. I think their reasons for saying that are ill-considered and moreover that what they're doing is apt to be mischievous and doing some real harm. So, I concocted a little thought experiment, a little intuition pump to suggest that. So this is the case of the nefarious neurosurgeon, who treats a patient who has obsessive compulsive disorder by inserting a little microchip in his brain, which controls the OCD, the obsessive compulsive disorder. Now, there is such a chip. It's been developed in the Netherlands and it works really quite well. That's science fact, but now here comes science fiction. So the neurosurgeon, after she's operated on the guy, sewed him all up, say, "Okay, your OCD is under control now you'll be happy to learn, but moreover our team here will be monitoring you 24/7 and we're going to be controlling everything you do from now on. You will think you have free will. You'll think you're making your own decisions, but really you won't have free will at all. Free will is an illusion that we will maintain while controlling you. Goodbye, have a nice life." Sends him out the door. Well, he believes her. She has a shiny lab and, you know, lots of degrees and diplomas and all that. So, what does he do? Well, he, thinking he doesn't have free will anymore, he gets a little self-indulgent, a little bit aggressive, little negligent in how he decides what to do. And pretty soon, by indulging some of his worst features, he's got himself in trouble with the law. And he's arrested and he's put on trial. And at the trial he says, "But your honor, I don't have free will. I'm under the control of the team at the neurosurgery clinic." They say, "What's this?" And they call the neurosurgeon to the stand. And say, "Did you tell this man that you are controlling his every move, he didn't have free will?" She says, "Yeah, I did, yeah, but I was just messing with his head. That was just a joke. I didn't think he'd believe me." Now, right there, I think we can stop, take a deep breath and say, well she did something really bad. That was...that was really, she really harmed that man. In fact, her little "joke," telling him that, actually accomplished non-surgically pretty much what she claimed to accomplish surgically. She disabled him by telling him he didn't have free will. She pretty much turned his free will off and turned him into a morally incompetent person.

Now, if we agree that she did a bad thing, if nobody recommends people play jokes like this, what are we to say about the neuroscientists who are telling the public every day, "We've shown in our neuroscience labs that nobody has free will." I think if the neuroscientists recognize that what my imaginary neurosurgeon did was irresponsible, they should think seriously about whether it's irresponsible of them to make these claims about free will. And it's not just a fantasy. Vohs and Schooler, in an important paper, which has been replicated in several different ways, set up an experiment, really to test this with college students, who were given two texts to read. One was a text. They were both from Francis Crick's book, "The Astonishing Hypothesis," and one was not about free will. And the other was about free will. And basically it said, "Free will is an illusion. All your decisions are actually determined by causes that neuroscience is investigating. You don't have free will. That's just an illusion." All right, so there we have two groups. The group that read that passage and the group that read another passage from that book of the same length. After they've read the passage, they are given a puzzle to solve where they can earn some money by solving it. And the experimenters cleverly made the puzzles slightly defective, so there was a way of cheating on the puzzle. That was, oops, inadvertently revealed to the subjects. And guess what? The subjects who'd read the passage where Crick says, "Free will is an illusion," cheated at a much higher rate than the other ones. In other words, just reading that passage did have the effect of making them less concerned about the implications of their actions and they became, as it were, negligent, or worse, in their own decision-making.