Evolutionary biologist David Barash, who describes himself as “an utter and absolute, dyed-in-the-wool, scientifically oriented, hard-headed, empirically insistent, atheistically committed materialist,” says that when he was asked which problem is the most difficult faced by science, there’s no question :

I answered without hesitation: How the brain generates awareness, thought, perceptions, emotions, and so forth, what philosophers call “the hard problem of consciousness.”

It’s a hard one indeed, so hard that despite an immense amount of research attention devoted to neurobiology, and despite great advances in our knowledge, I don’t believe we are significantly closer to bridging the gap between that which is physical, anatomical and electro-neurochemical, and what is subjectively experienced by all of us … or at least by me. (I dunno about you!)

… [T]he hard problem of consciousness is so hard that I can’t even imagine what kind of empirical findings would satisfactorily solve it. In fact, I don’t even know what kind of discovery would get us to first base, not to mention a home run. Let’s say that a particular cerebral nucleus was found, existing only in conscious creatures. Would that solve it? Or maybe a specific molecule, synthesized only in the heat of subjective mental functioning, increasing in quantity in proportion as sensations are increasingly vivid, disappearing with unconsciousness, and present in diminished quantity from human to hippo to herring to hemlock tree. Or maybe a kind of reverberating electrical circuit. I’d be utterly fascinated by any of these findings, or any of an immense number of easily imagined alternatives. But satisfied? Not one bit.

Todd Gitlin reacts, sensibly:

I think it is a matter of intellectual honesty to reconcile with the existence of the unknowable. We don’t see around corners. So be it. A science that can’t acknowledge that total knowledge is a fool’s project is dangerous.

I am reminded of this fascinating 2007 interview with Steven Pinker and his wife Rebecca Newberger Goldstein, in which they discussed their atheist materialism, and what would make them abandon it:

Virtually all religious believers think the mind cannot be reduced to the physical mechanics of the brain. Of course, many believe the mind is what communicates with God. Would you agree that the mind-brain question is one of the key issues in the “science and religion” debate?

PINKER: I think so. It’s a very deep intuition that people are more than their bodies and their brains, that when someone dies, their consciousness doesn’t go out of existence, that some part of us can be up and about in the world while our body stays in one place, that we can’t just be a bunch of molecules in motion. It’s one that naturally taps into religious beliefs. And the challenge to that deep-seated belief from neuroscience, evolutionary biology and cognitive science has put religion and science on the public stage. I think it’s one of the reasons you have a renewed assault on religious beliefs from people like Dawkins and Daniel Dennett.

The neuroscientific worldview — the idea that the mind is what the brain does — has kicked away one of the intuitive supports of religion. So even if you accepted all of the previous scientific challenges to religion — the earth revolving around the sun, animals evolving and so on — the immaterial soul was always one last thing that you could keep as being in the province of religion. With the advance of neuroscience, that idea has been challenged.

Some prominent scholars of the mind have not adopted the strict materialist position. The atheist Sam Harris, who’s a neuroscientist by training, says he’s not at all sure that consciousness can be reduced to brain function. He told me he’s had various uncanny — what some would call telepathic — experiences. And there’s David Chalmers, the philosopher, who’s also critical of the materialist view of the mind. He has argued that the physical laws of science will never explain consciousness.

GOLDSTEIN: It’s interesting. Actually, my doctoral dissertation was on the irreducibility of the mind to the physical. We have not been able to derive what it’s like to be a mind from the physical description of the brain. So if you were to look at my brain right now, I would have to tell you what it is that I’m experiencing. You can’t simply get it out of the physical description. So where does that leave us? It might mean that we’re not our brain. It might mean that we have an incomplete description of the brain. Our science is not sufficient to explain how this extraordinary thing happens — that a lump of matter becomes an entire world. But the irreducibility doesn’t in itself show immaterialism. And you can turn it around and say, look, all the neurophysiology that we have so far shows there is a correlation between certain physical states and mental states. And even a dualist like Descartes said there’s a one-to-one correlation between the physical and the mental. So I’m not sure that we’ve settled this question once and for all.

PINKER: I’m also sympathetic to Chalmers’ view. It might not be the actual stuff of the brain that makes us conscious so much as it is the information processing. I don’t think Chalmers’ view would give much support to a traditional religious view about the existence of a soul. He says that consciousness resides in information. So a computer could be conscious and a thermostat could have a teensy bit of consciousness as well. Still, the information content requires some kind of physical medium to support the distinctions that make up the information. And the Cartesian idea that there are two kinds of stuff in the universe — mind and matter — doesn’t find a comfortable home in current views of consciousness, even those of Chalmers.

I know neither of you believes in paranormal experiences like telepathy or clairvoyant dreams or contact with the dead. But hypothetically, suppose even one of these experiences were proven beyond a doubt to be real. Would the materialist position on the mind-brain question collapse in a single stroke?

PINKER: Yeah.

GOLDSTEIN: Yeah, if there was no other explanation. We’d need to have such clear evidence. I have to tell you, I’ve had some uncanny experiences. Once, in fact, I had a very strange experience where I seemed to be getting information from a dead person. I racked my brain trying to figure out how this could be happening. I did come up with an explanation for how I could reason this away. But it was a very powerful experience. If it could truly be demonstrated that there was more to a human being than the physical body, this would have tremendous implications.

Many stories of the paranormal turn on anecdotal, once-in-a-lifetime experiences. They fall outside the realm of what scientists can study because they are not repeatable. That raises the question, does science have certain limits to its explanatory power? Might there be other parts of reality that are beyond what science can tell us?

PINKER: It’s theoretically possible. But if these are once-in-a-lifetime events, one has the simpler explanation that they’re coincidences. Or fraud.

GOLDSTEIN: Or wishful thinking.

PINKER: Statisticians tell us that people underestimate the sheer number of coincidences that are bound to happen in a world governed by chance. That’s why it would be essential to do the statistician-proof experiment or the Amazing Randi-proof experiment, showing that it isn’t just stage magic. If that could be done, if you could show that someone could know something without it having to go through their sense organs — that you could cut the optic nerve connecting the eyes to the brain and the person could still see. Then, yeah, everything that I’ve been saying would be refuted. The fact that we don’t have reliable paranormal phenomena, the fact that all aspects of our experience do depend on details of the physiology of the brain, make it a persuasive case that our consciousness depends on the brain.

GOLDSTEIN: Yeah, but what you’re saying could be very true. It could be in the nature of the phenomena that it’s extremely difficult to reproduce it in controlled experiments. In which case, we’ll never know. I think it’s a kind of arrogance to say that our science is complete. It’s an amazing thing that we can know as much about the physical world as we do know. Why assume that we know everything about the world that there is to know? We’ve developed through all sorts of happenstance a kind of methodology that allows us to know a tremendous amount. It’s an extraordinary thing that we can test and probe nature. And it’s yielded amazing secrets. But why assume that this methodology that we’re just damn lucky to have been able to stumble upon is going to yield all secrets? Of course, there could be things beyond the reach of science. But could we have any good evidence for accepting it? As soon as you have good evidence, it becomes science. So can there be good evidence for non-scientific propositions? No. Because the minute there is good evidence, it becomes science.

I am reasonably certain that no demonstration of the paranormal would be enough to satisfy Pinker and Goldstein, to the point where they abandoned their materialism.