At a meeting I recently attended in Switzerland, “The Enigma of Human Consciousness,” two prominent physicists talked about the limits of science. One was Martin Rees, whom I wrote about in a recent column. The other was Marcelo Gleiser, a professor at Dartmouth. Gleiser, who grew up in Brazil and still speaks with an accent, is a big-picture guy, with a knack for gracefully, even poetically, reflecting on science’s philosophical implications. He describes himself as “a metaphysician disguised as a theoretical physicist.” He contributes to the National Public Radio blog “Cosmos and Culture,” and he has written five popular books. In Switzerland, Gleiser reprised themes of The Island of Knowledge, which meditates on the paradoxical manner in which our sense of mystery grows in proportion to our knowledge. I liked Gleiser’s view of science, which resonates with my own, and I liked Gleiser, whose intellectual style is somehow both bold and gentle. He reminds me of my pal Tyler Volk. Gleiser and I recently had the following email exchange. —John Horgan

Horgan: Why physics?

Gleiser: Physics has allowed me to think deeply about some of the most fundamental questions we can ask— the nature of space and time, the relationship between mind and reality—while offering a beautiful vision of matter as energy patterns in constant flux. That we can make sense of some of these patterns and create mathematical models that describe and even predict their behavior is, to me, absolutely amazing. I guess I’ve always been a metaphysician disguised as a theoretical physicist.

Horgan: Did growing up in Brazil give you a different perspective on science?

Gleiser: I think so, especially because I grew up in Rio, where nature is simply everywhere. The city is squeezed between very dramatic old mountains covered with exotic Atlantic tropical forest (well, the surviving patches of it) and the ocean. Growing up at Copacabana beach allowed me to look at the horizon every day, a privilege. The horizon always intrigued me as a child, unattainable, the impossible line where ocean and sky meet, both a representation of the curvature of our planet and of infinity. It’s there and it isn’t, a way reality plays with our senses. Culturally, the mixing of different worldviews that characterize Brazilian life also played a huge role. I understood early that there are many ways of seeing the same thing, and each carry meaning in its own way.

Horgan: You devote a lot of energy to writing and talking about science for the public. Is there any message you are especially keen on imparting?

Gleiser: The main message is the awesomeness of the scientific worldview; that we can make sense of so much of the world around us in ways that have transformed, over and over again, how we live and understand who we are in the cosmos. I see science as a transformative cultural force and want to share what we know of the world with the largest possible number of people so that they can not only appreciate the beauty of it all but also be informed citizens empowered to make well-informed decisions about their lives and our collective future.

Horgan: Do any pop-science claims or tropes really bug you?

Gleiser: Yes, actually, quite a few. For example, claims that we understand the big bang, the event that marked the origin of the universe. We most certainly do not, and I go further to claim that we cannot, given the way science depends on a conceptual framework to operate. Science can give at most an incomplete answer to the question of the origin of everything, one that depends on notions such as space, time, energy, laws of nature… Another one is the claim that we “live in a multiverse.” We have no clue if a multiverse exists or not, and, worse, we wouldn’t be able to know either way. Science popularizers often get carried away and present ideas that are grounded on speculation as a done deal. We must be very careful with that, especially in a time when science’s credibility is constantly under attack. Scientists don’t want to be the ones who undermine science’s credibility, presenting speculative ideas as confirmed scientific facts!

Horgan: At the meeting we attended recently, Martin Rees speculated that science might be bumping into limits and might never explain consciousness and other emergent phenomena. What do you think?

Gleiser: I think that Martin is correct, not so much in saying that science is bumping into limits but in arguing that science has limits. These are different things. There is no doubt that there are many reasonable scientific questions that we cannot answer. I gave two examples above; another is knowing how life originated on Earth. Unless we can prove a theorem that there is only one or very few biochemical pathways from nonlife to life, we can’t be certain of what happened here some 4 billion years ago. To appreciate the beauty of science, it is essential to understand how science operates and why it has limits. It is a human creation, after all. We measure natural phenomena with instruments of all sorts, and they all have precision limits and ranges. We can’t see what’s beyond, and even if we improve their precision constantly, there is always a little more to go. Knowledge is an endless pursuit, at least as long as we can ask questions and be funded to try and answer them. Science creates a self-improving description of nature, but one that we cannot hope will ever be final, a point I explored in my book The Island of Knowledge.

Horgan: Will we ever know why there’s something rather than nothing?

Gleiser: I don’t think we can, at least not through science only. This reverts to the problem of the First Cause, which is the uncaused cause that gave rise to all other causes. We humans think along causal chains, and can’t figure out how something came about and started the game. Claims that quantum physics can do that, as in the “universe out of nothing,” miss the fundamental point that we must assume these theories to start with. The question then becomes why these laws and not others in this universe? And if we appeal to a multiverse to try to answer this, we tangle ourselves in even more knots, given that we can’t know whether a multiverse exists. Science doesn’t need to explain the origin of everything. It does an awesome job describing many other natural phenomena, and there is plenty to think about. This expectation comes from trying to equate science with some kind of new religion, a grave mistake in my opinion.

Horgan: Should physicists give up the quest for a unified theory?

Gleiser: I love that you called this a “quest”. Sounds very chivalric, right? Scientists will find the answer to our deepest questions, in a sense becoming the new holy men, the shamans of modern society. However, this quest is impossible to accomplish. Given how science operates, the best that we can hope for is to find unifying explanations of what we know now of the world. We’ve done a pretty good job with gravity and electromagnetism, but seem to be stuck bringing in all four fundamental forces together. But even if we did, and it’s a big if right now, this “unified theory” would be limited. For how could we be certain that a more powerful accelerator or dark matter detector wouldn’t find evidence of new forces and particles that are not part of the current unification? We can’t. So, dreamers of a final theory need to recalibrate their expectations and, perhaps, learn a bit of epistemology. To understand how we know is essential to understand how much we can know.

Horgan: Can information theory help physics advance?

Gleiser: Definitely. Information is the modern intellectual currency. We are reframing everything in terms of information, from the physics of black holes to data science dedicated to finding out what you want to buy next. Information theory can help us understand the complexity and variety of shapes in nature, from atoms to trees to galaxies--what I like to call shape complexity-offering an incredibly rich way to discern organizational patterns of matter and their properties. I’m really excited to be working on this right now.

Horgan: Are you a fan of the new theory of consciousness, integrated information theory?

Gleiser: I think a “fan” would be too strong a word, but I applaud Tononi and collaborators for trying to come up with a quantitative way of making sense of consciousness. Of course, the essential premise of IIT is that consciousness is fundamental, sort of like as fundamental as space and time (assuming these two are fundamental, another story altogether). I find it hard to understand what that even means, as it focuses on ontology, what is real and what is not. I am more of a science-as-a- descriptive-tool kind of person, and see consciousness in a more pragmatic and less fundamental way, as an emergent property of very complex neuronal patterns. Of course, I could be wrong and we may indeed need a very new perspective on the nature of consciousness. Even so, I don’t think making it just a mathematical theory will be enough. As with the origin of the universe, the nature of human consciousness may be the kind of question that we may not be well-equipped to answer fully through a scientific approach, even if we are able to artificially create some kind of limited consciousness through AI. This doesn’t mean that consciousness has anything to do with supernaturalism; it simply means that some questions are not well-posed for our current scientific framework.

Horgan: Will the weirdness of quantum mechanics ever go away?

Gleiser: I don’t see how. It is by now clear that nonlocality is here to stay, the notion that quantum entanglement seems to defy space and time, as entangled particles behave as one at very large distances and faster than the speed of light. Also, quantum indeterminacy is fundamental, in that we cannot predict what value we will measure in a quantum system. I am happy to embrace the mystery of quantum mechanics without having to force reality into it, as some colleagues do by attributing reality to the wave function (ontology again!) at the expense of suggesting that every measurement creates a set of parallel universes so that all options are realized somewhere. When the solution to a mystery is even more mysterious we should be very careful… I see quantum mechanics as a powerful way to describe what we can measure of the world of the very small. Does it create an interpretation nightmare? Yes, it does. But it also reflects our very incomplete knowledge of the world, something that is not our enemy. Should we keep pushing forward? Of course! To me, the fundamental mystery is how the observer and the observed are tangled up, the issue of how measurements gives reality to a quantum object. We don’t know if the moon is there when we are not looking, but we assume it is. Assuming it’s there is not the same as knowing it is there. Science often forgets how experience is absolutely essential to everything we do. Perhaps that’s the missing link in quantum mechanics, understanding it as a narrative of the self interacting with the world.

Horgan: Do you believe in God?

Gleiser: I position myself as an agnostic. I don’t see evidence for any kind of supernatural being or intervention, but also understand that we are partially blind to what’s out there and hence should show some humility. I see atheism as being inconsistent with the scientific method, as it is, essentially, belief in nonbelief. It does not offer any proof of nonexistence as that would be literally impossible through science. Atheism elevates belief to a rational argument that is very ill-founded epistemologically. You may not believe in God, but to affirm its nonexistence with certainty is not scientifically consistent. If you are nonbeliever, the only position consistent with science is agnosticism.

Horgan: What’s your utopia?

Gleiser: My utopia is that in the next decade we are going to see a rebirth of our humanity, a moral uprising where our relationship with life, human and all other creatures, and with our planet will become the new universal moral imperative. We need to change and fast the way we eat and the way we relate to our planetary resources. In my utopia, this will still happen in my lifetime.

Further Reading:

The Weirdness of Weirdness

Is Science Infinite?

Was I Wrong about “The End of Science”?

See also Q&As with David Deutsch, Steven WeinbergGeorge EllisCarlo RovelliEdward WittenScott AaronsonSabine HossenfelderPriyamvada NatarajanGarrett LisiPaul SteinhardtLee SmolinStephen WolframRobin HansonEliezer YudkowskyTyler Volk, Stuart KauffmanChristof KochRupert Sheldrake and Sheldon Solomon.