You might think such a shortfall would produce a certain intellectual humility, some thoughts along the lines of: what do I really know? But that doesn't seem to have happened in the case of Professor Greene, as he feels confident enough to tell us that we don't really have such a thing as free will.
The reason given by Greene in this interview is that everything has to have a “fundamental microphysical underpinning.” Greene says, “When I move my teapot, that sensation is absolutely real,. But that's all it is. It's a sensation."
This is not a coherent argument against free will. First, we know of incredibly important phenomena that do not occur for microphysical reasons, including the effects of gravitation (gravitation has no detectable effects on any microscopic or subatomic scale, nor any known microphysical cause). Secondly, it is entirely possible that consciousness and free will might have a microphysical underpinning.
In the case of a common-sense thing such as free will, the burden of proof is on the skeptic. Since almost all of us intuitively feel that we do have free will, if you're going to try to overturn that common-sense assumption, you'd better have a pretty good argument, rather than just some lazy phraseology.
Earlier this year Greene gave an interview in which he stated this argument against free will:
But as a snapshot, if you look at the equations that we have today, there does not seem to be a place anywhere in those equations where you say, oh, OK, and here is where human free will comes in to how things are going to evolve. Right? There’s no term in the equations where that happens.
This seemed to produce a laugh from the interviewer, as well it should have. For a physicist to argue that free will doesn't exist because he doesn't see it in his equations is like a biologist arguing that love doesn't exist because he doesn't see it in his microscope.
The equations of physicists describe certain relations between quantifiable aspects of our universe, involving matter, energy and forces in our universe. There is not the slightest reason to think that a physics equation would or could ever refer to some unquantifiable thing such as free will.
Physics isn't just equations, but also experiments. When we look at some of the more interesting physics experiments, we actually see things that mesh well with the concept of free will. In the famous double-slit experiments (well described in this video), particles behave differently depending on whether or not they are observed. In one of these experiments, when electrons are being observed, they act like particles, but when they are not being observed they act like waves. Although the experiment doesn't prove anything directly about free will, it suggests that the behavior of particles is directly affected by human consciousness, rather than the deterministic idea that we are merely “particle pawns” riding in the back seat with physics always being in the driver seat.
The experiments described here indicate that human thought has the ability to change the interference patterns produced in the double slit experiment, which again suggests that the human mind can causally affect microphysical phenomena, rather than the idea that our thoughts or choices are merely things that are passive products of such phenomena.
When it comes to free will, Greene's attitude seems to be: I can't believe in that, because I don't see it in my equations. But Greene throws away such a rule when it comes to things infinitely harder to believe in than free will. For Greene has written a book called The Hidden Reality talking enthusiastically at great length about claims such as parallel universes and vast collections of other universes. Of course, there is no verified equation that gives support for any such ideas. Equations deal with quantifiable physical things in our universe, so an equation could never support a conclusion about a parallel universe or another universe.
Why the double standard? I think it may come down to dollars. Speculating about parallel universes and other universes is a lucrative little cottage industry for many a modern physicist, a nice safe way to boost your salary. All a modern physicist needs to do is write a book on the topic, and he runs no risk at all that anyone will prove him wrong (since no could ever prove or disprove these ridiculously speculative theories). So while Greene gets all minimalist and skeptical and parsimonious when it comes to free will (denying it on the basis that it's not in the equations), he goes a million miles in the completely opposite direction when it comes to parallel universes and other universes, setting forth on endless ultra-extravagant speculative flights of fancy, much of it fit for pulp science fiction magazines. Very inconsistent, but at least it rakes in the royalties.
In this interview Greene ties together his rationale for rejecting free will with his affection for parallel universes. Greene says:
"We do not see free will in the equations: you and I are just particles governed by particular laws. Every individual, faced with five choices, would make all five -- one per universe. And all of the choices would be as real as the others."
Besides being morally poisonous (a perfect prescription for moral indifference), this seems like one of the looniest statements I have ever heard a physicist make. As I discuss here, there is no evidence or good argument to support such fatuous thinking (just as there is no evidence to support the string theory that Mr. Greene has been selling for so long).
So are you a mere pawn of physical laws? No, you are not. You have free will that is as real as your own consciousness. If you commit a moral error, you cannot use the excuse of “the physics made me do it.”