From Frank Wilczek, Nobel laureate and a professor of physics at the Massachusetts Institute of Technology’s Center for Theoretical Physics:

Is there a final theory of everything? The answer depends on what you mean by “final” and “everything.” And, for that matter, “is.” Let’s consider.
What could we mean by a “final theory”? A theory is final if it is perfectly adapted to its subject matter, so that there is no point in trying to improve it. What was a frontier outpost of knowledge becomes a settled bastion. Unfortunately, experience teaches us that what appear to be “final” theories have a disconcerting tendency to unravel. Euclidean geometry, which seemed to Kant so firmly established that he took it to be an a priori precondition for perception, turned out to be a special, limiting case of possible geometries. And not the one chosen by Nature! Newtonian mechanics went from triumph to triumph, deriving amazing consequences (Neptune!—the original “dark matter”) from simple, well-tested hypotheses. Yet in the 20th century, first special relativity rocked, then quantum theory mocked, Newtonian principles. Today, classical thermodynamics, quantum electrodynamics (QED), and quantum chromodynamics (QCD) appear to be final theories. So too, in a different way, do the big-bang theory of cosmology and the evolution theory of biology. Professionals work to apply, develop, or add to them—but change them? Not so much.
What could we mean by a “theory of everything”? The literal meaning is silly: There will never be a theory that covers everything, or even that shared part of everything we call the natural world. The instabilities of mathematical chaos and the indeterminism of quantum mechanics would inject big elements of contingency and accident into the description of the actual world, even if we were to have a perfect understanding of its equations and starting principles. In practice, our ability to formulate questions far outstrips our ability to solve equations. No combination of theory and pure thought will encompass everything: The future will always bring surprises (e.g., weather!); historiography will always require archives and relics.
A more realistic, rigorous interpretation of “theory of everything” involves the idea of completeness. A theory that derives everything true (and nothing false) in a sharply defined domain of discourse is complete for that domain. Competent experts think that classical thermodynamics, QED, and QCD are complete theories for governing conditions for equilibrium among macroscopic phases of matter, chemistry, and nuclear physics, respectively. In all these cases, the theories do not cover historical questions: For example, QED does not tell us what substances we actually find on Earth, but rather what the possible substances are and how they will behave. Thus, we have good models for what complete theories of parts of reality look like. They are reductionist theories, in the sense that they supply precise mathematical laws for the behavior of underlying building blocks, from which the behavior of larger, more complex objects can be derived (in principle; as a practical matter, especially in QED and QCD, we can only “solve” the equations—i.e., determine their consequences by direct calculation—approximately and in very simple cases. Physicists have not put experimental chemists out of business!) Is there a complete theory, in the same reductionist sense, whose domain is everything?
At this point, we have to face the question Bill Clinton made famous: What do we mean by “is”? Any good dictionary suggests several alternative meanings. For us, the important distinction is between “is” as “presently existing” and “is” as “existing in principle.”
If we use “is” in the first sense, then the answer to our question is very easy: No, there is not a final theory of everything. The established laws of physics, while extremely impressive and successful across a very broad range, are widely perceived to be imperfect and incomplete. They postulate four distinct basic forces (gravity, electromagnetism, strong, and weak) and several distinct kinds of matter (quarks and leptons in a dozen varieties, gluons, photons, W and Z particles, gravitons, Higgs bosons …); we yearn for more unity and coherence. They do not account for the astronomers’ dark matter and dark energy. They break down in the earliest moments of the big bang, and at the centers of black holes. We have some brilliant, promising-looking ideas for improving the situation (e.g., extended gauge symmetry, supersymmetry, axions). The Large Hadron Collider will (I hope!) confirm some of those ideas and suggest new ones. But I don’t foresee that physicists will come close to answering all these basic questions anytime soon. So there won’t be a theory of everything, even in the narrow sense. And we won’t stop trying to do better, so there won’t be a final theory, either.
If we use “is” in the second sense, the answer is less easy, and reasonable people might differ. Is there a “final theory of everything” out there in some idealized world of ideas, waiting to be discovered? My own opinion is that there is such a theory, but that it won’t live up to its billing. Our successes so far give us every reason to think that there are basic, precise mathematical laws governing the elementary processes of Nature, and that, in principle, they cover everything—no physical phenomenon eludes their grip. And people will construct ever more comprehensive reductionist theories, which realize more and more of that ideal. Eventually, however, they will stop making progress, and (implicitly or explicitly) establish an existing theory as “final.” But that “final theory of everything” won’t help to predict the weather, or the possible species of beetles, or much of anything interesting about human beings. For better or worse, the theories of physics we have today already contain everything that fundamental physics has to offer on those topics.

Frank Wilczek appears with Steven Weinberg, David Gross, Leonard Susskind, Lawrence Krauss, Robert Laughlin, Lee Smolin, and Stephen Wolfram in “Is There a Final Theory of Everything?” the 31st episode in the Closer to Truth: Cosmos, Consciousness, God TV series. The series airs on PBS World (often Thursdays, twice) and many other PBS and noncommercial stations. Every Friday, participants discuss a recent episode.

From Robert Lawrence Kuhn, host and creator of Closer to Truth:

Most people believe that God exists and intervenes actively in the world—answering prayers, making miracles, even ordaining history. But if God does exist, this intervening-kind of God, how does this God intervene? What possibly could be God’s mechanism for making things happen? Fiddle with each and every atomic particle? Adjust each and every nuclear force? Command all particles and forces en masse? The physical universe seems closed and complete, so how could something not part of it—God by definition is nonphysical—affect it? How could God interact with the world?
Robert John Russell, founder of the Center for Theology and the Natural Sciences, states that there are at least four ways in which God interacts with the world: (i) creating and sustaining the world (“T [time] equals 0”); (ii) through natural processes (“The regular laws of physics and biology are God’s action… one can call this ‘general providence.’”); (iii) special events of significance (“where God acts to make a difference but which scientists see as part of the flow of nature,” which can be “special providence”); (iv) miracles (“where God’s action goes beyond the ordinary routines of nature”).
Russell, who is an ordained minister with a doctorate in physics, likes to explore the third way and tease out meaning. In the past, he says, the dichotomy “between objective and subjective divine action was forced because we thought we lived in a world which was governed by deterministic laws, a lock-step, billiard-ball, clockwork world.” Quantum mechanics, Russell suggests, “at least re-opens the question of whether or not we’re forced to continue with that split in our theological choices. … And that’s a genuine research question.”
How to progress? Russell states, “The first step is to say God is acting through all the laws of nature. So whatever happens, God is involved in it. Now because there is no sufficient natural cause [when choices are made in quantum mechanics], so God’s action could be thought of as special because God is acting on those events in special ways; that is, God is determining, because nature doesn’t, whether a photon bounces off the surface of water or goes through it.”
Would that not be God’s active intervention? No, Russell argues, “It’s an act. It’s not ‘intervention,’” because he uses the term “intervention” in a technical sense to mean “God violates the laws of nature.” And thus he stresses that “God was clever enough to create a universe which is quantum mechanical, which allows God to be acting all the time.” Following the consequences of this line of thinking, Russell observes that “the distinction between general providence, category two, and special providence, category three, kind of breaks down because God is truly acting all the time at the level of quantum mechanics.“ In this way, Russell claims to eliminate the “artificial distinction” between God’s overall purposes going on continuously and God’s special purposes, which are occasional events. God is acting all the time.
This strange land is home for John Polkinghorne, who was a quantum physicist at Cambridge University, when, in the middle of his scientific career, he decided to study for the priesthood. Today, he is recognized worldwide as a thought leader in science and religion. He too speaks about “the intrinsic unpredictabilities present in physical process … discovered first through quantum theory and then later on through chaos theory.”
But in contemplating God’s action in the world, Polkinghorne begins from a different perspective. He references something familiar, perhaps so very much familiar that we miss its deep significance—what he calls “the fundamental human experience of agency.”
“I, as a whole person, decide to raise my arm,” he says. “I believe that we interact with the world in this sort of top-down way.”
Polkinghorne then draws his analogy. “Now if we interact with the world in a top-down way, it seems to be entirely credible that the world’s Creator also can interact with the world and bring about events in a similar top-down way. So I have a picture in which God interacts with unfolding process, allowing creatures to explore the range of possibilities, but also preserving some providential room so that he as Creator can maneuver in bringing about the future.”
Polkinghorne admits that “it’s a complicated picture,” and “we can’t disentangle it because if things are unpredictable, you can’t parallel park and say: Nature did this, humans will did that, God did those other things—but nevertheless all these influences are at work in the world. That’s a perfectly coherent and believable picture and it’s the one I hold.”
Ernan McMullin, a well-known philosopher of science (a Catholic priest trained in physics and former chair of philosophy at Notre Dame), believes in the same Judeo-Christian God as do Russell and Polkinghorne, but as for explaining how God interacts with the world, he differs sharply. “I don’t see quantum theory as answering it, chaos theory even less so,” McMullin asserts. “Of the available menu of theories we have at the present, I don’t see any of them as very promising for giving us a way in which God inserts special action in the world. It’s as though God is moving behind the scenes and has to find a way of influencing what is his very creation.”
To McMullin the answer is stunningly simple: “God affects the universe by making it be! If one accepts the postulate of creation, then in fact the universe is the product of a single act of creation—and that’s how God influences the universe. My goodness, what a powerful influence that is! The point here is not a matter of asking how could God sort of work within this universe and not, so to speak, upset the laws of physics. The point is that God has in fact produced the universe and that simple act of creation is the most powerful influence you could have.”
Thus McMullin says he has “no difficulty with miracles at all because if in fact we have a universe which is the product of God, and in which the mere continuance of the law of gravity is God’s choice, the fact that at some point the law of gravity could be suspended, well, of course a creator can do that!” According to McMullin, a sophisticated thinker, “It’s simple! The way by which God works in the world is by being the creator of that world in the first place. It’s not a matter of intervening. It’s a matter of making that kind of world to begin with, a universe within which at a certain point this or that would happen.” (McMullin takes pains to emphasize that “what I do find difficult is to discern when and where miracles actually did occur—that’s the tough one.”)
Russell, Polkinghorne, and McMullin are traditionally and proudly Christian, which no doubt affects their views. Not so cosmologist Paul Davies, who has iconoclastic ideas about “purpose” in the universe (in his view, “the universe is ‘about’ something”). Davies accomplishes the neat trick of opposing both theists and materialists.
“I’ve always had a problem about a God who’s a miracle-working super-being, a cosmic magician,” Davies states. “I often say that there are no miracles except the miracle of nature itself. And so if I use the word ‘God’—which I’m always very careful about because it carries so many different meanings—it is in terms of the meaningfulness of the whole package, not in terms of a being who is sort of meddling from time to time.”
Speaking as a scientist, Davies says, “the idea of a God who intervenes actively in history—through prayer, working occasional miracles—is really pretty horrible and I wouldn’t want that.”
Davies has a better idea, he says, a “challenge” for “God,” as it were. “Come up with some deep mathematical principles, something of that sort, and then let it go. Let the universe generate its own life, its own self-awareness, so that the whole thing self-organizes and self-complexifies. No meddling, tinkering, making things happen by fiat. That’s much, much harder.”
To Davies, the universe as a self-generating, self-observing, self-organizing and self-complexifying thing “looks really deeply ingenious, really clever.” On the other hand, “a cosmic magician looks like just a conjurer,” he emphasizes, “so I can’t have much respect for such a being.”
But the traditional personal God who knows and cares for us is appealing.
Can that kind of God be saved?
Alvin Plantinga, one of the world’s leading Christian philosophers, is not at all embarrassed by God’s interventions. “People argue that special divine action can’t happen because it conflicts with the laws of conservation of energy [and mass],” Plantinga says. “If God, say, were to create a full-blown horse in the middle of the Notre Dame campus, this would violate all these conservation laws. But this is not in fact correct. The conservation laws are stated for closed systems, where there is no energy input from outside the system. But, of course, if God were to create a horse right here, then no system that includes that horse would be a closed system because such a system would, by definition, have this influx of energy from the outside, which is God creating the horse.”
But isn’t the universe in totality a closed system? “The material universe as a whole is a closed system,” Plantinga responds, “but if God acts in it, then it’s no longer a closed system. And it’s not part of physics to assert that God doesn’t act in it. That’s not a physics truth or a physics claim. That’s a theological truth or claim.”
Plantinga’s argument may sound simplistic or circular, but it strikes me as possibly profound. If God intervenes in the universe, then that very act causes the universe not to be a closed system, thus voiding any violation of the laws of conservation of energy and mass.
Where then with God’s interaction? For the sake of the argument, I’ll assume God exists. So I then ask, in what way could a nonphysical being intervene in the physical world? Because if there is no way that such intervention can make coherent sense, then I must question the initial assumption that God exists.
One view is that God just suspends his own laws. I guess that’s possible. But then wouldn’t God be distorting the natural functioning of God’s own world?
What about the contemporary idea that God’s place of action lies in the scientific “gaps” of unalterable uncertainty—quantum mechanics and chaos theory—where clockwork determinism does not hold?
I pause and wonder … but quantum uncertainties seem truly random and chaos theory seems more a lack of knowledge, so neither seems ideal as that super-special place for God to work his wonders.
For me, for now, I can come to only one conclusion: If a nonphysical supreme being, “God,” does exist, and if God does intervene in the world, I’d be surprised if we could ever figure out how.

Robert Lawrence Kuhn speaks with Nancey Murphy, John Polkinghorne, Robert Russell, William Dembski, Paul Davies, Alvin Plantinga, and Ernan McMullin in “How Could God Interact With the World?” the 30th episode in the Closer to Truth: Cosmos, Consciousness, God TV series. The series airs on PBS World (often Thursdays, twice) and many other PBS and noncommercial stations. Every Friday, participants discuss a recent episode.

From science fiction writer and space physicist David Brin:

Way back, two-thirds of a century ago, shortly after the Manhattan Project to develop the atom bomb, physicist Enrico Fermi and his colleagues took a break, over lunch, to discuss the notion of other life in the cosmos.
Many of Fermi’s colleagues enjoyed science fiction stories. They held that a richly endowed cosmos, replete with trillions of stars, should contain a vast plurality of living worlds, and—on some of them—minds like ours, capable of insight, curiosity, intellectual advancement. Within a galaxy as old as this one, there must have been many, many races that preceded us, some of them now millions of years older, and commensurately more advanced. Indeed, some of these alien intelligences would surely have set forth, expanding and exploring across space. How interesting a future we would have, with such fascinating others to talk to, when our descendants finally made contact!
Fermi listened patiently to these expressions of confidence in a fecund universe, teeming with conversation, as vivid and enthusiastic as the discussion they were having at that moment, in a Chicago cafeteria. Only then, the great physicist shook his head and asked:
“So? Shouldn’t they already have been here by now? Should we not have heard their messages? Or seen their great works? Or stumbled upon residue of past visits to our planet? These wondrous ancients of yours, where are they?”
Across all the years since Fermi posed that challenge, it has been called many names. The Great Silence, the Seti Dilemma, and so on. But most often the “Fermi Paradox.” And every passing year, while enthusiasts still scan for signals, the sky’s eerie hush steadily gets more and more bothersome.
How many life-bearing worlds are out there? So curious are we—members of an expansive, eager, enlightenment civilization—that we are willing, even in rough economic times, to fund ambitious efforts like NASA’s new Kepler Orbiting Observatory, with the mission of putting solid numbers behind some of our best estimates. So far, it seems that planets are common in the cosmos. Now we hope to get a handle on what fraction may be a bit like Earth. But even if we find that figure to be high, it will take later, more advanced instruments, to detect glimmering spectroscopic indications that life appeared on those distant worlds.
And from there the conundrums will continue! What portion of these Life Worlds will develop intelligent, technological beings? (It only happened once on Earth, across 4 billion years.) And what further sub-fraction might eventually overcome all obstacles and hazards to start spreading across the stars?
These estimates have been crunched and probed and argued-over for more than two generations. Earnest calculations claim there ought to be neighbors out there. We shouldn’t be alone.
And yet, somehow, we appear to be! At least, as far as we can tell, so far.
Then it began to sink in. This wasn’t just a theoretical matter, anymore. The appearance of scarcity has implications, disturbing ones.
Something must be suppressing the outcome. A “filter” of some sort may winnow down the number of sapient races. To a number that is low enough to explain our apparent isolation. Our loneliness. Perhaps even reducing the total down to just one.
This is no place to get into the full-pitch debate. But over 10 dozen pat “explanations for the Fermi Paradox” have been offered. More than a hundred! Each of them pushed with great fervor by this or that person or group, each of them fervently convinced that the (skimpy) evidence supports just one possible conclusion.
Some claim that our fertile and lush planet must be unique. (And, so far, nothing like Earth has been seen, though life certainly exists out there.) Or, it is suggested that most life worlds suffer lethal accidents—like the one that ended the reign of the dinosaurs—far more often than our planet has. In other words, Earth has been luckier than most.
Other theories suppose that intelligence must be a rare fluke, and that fact alone would bring the numbers down to a level compatible with observation.
Note that these are actually the optimistic explanations! Because they suggest that the “great Fermi filter”—the thing that’s been keeping the numbers down—lies behind us. Not ahead.
But what if life-bearing planets turn out to be common? And suppose intelligence arises frequently? Then the filter—whatever process it is, that winnows down the numbers—may lie ahead of us. Perhaps some terrible mistake that all sapient races make. An error so alluring that all of them stumble into it. Some catastrophe that now awaits us, around the next bend.
Or perhaps several. A veritable minefield of possible ways to fail.
Want to hear something strange? The so-called “optimists” in the SETI (Search for Extraterrestrial Intelligence) community are more likely to believe something like this. Carl Sagan thought that most alien civilizations destroyed themselves through nuclear winter, unless they managed first to cure themselves of all aggressiveness … which might then explain why such species did not travel far or make colonies or fill the cosmos with their progeny. A pretty dour version of “optimism”!
That is the dour context of our story. And the implications go far, far beyond mere sci-fi musings about contact with aliens. In the end, all of this carries huge and important implications about us! Because now we have to wonder, each time we face some worrisome step along our road toward maturity … from avoiding war to becoming planetary eco-managers, to genetic engineering and so on. … All the time, we have to ask ourselves “Could this be it? The mistake? The big one that all (or almost all) alien sapient races make? The error, the trap, that keeps the numbers down and that keeps us asking Fermi’s question?”
It is the specter lurking at our banquet. The shadow that slinks around the edges of both reflection and foresight, as we turn to examine all the conceivable threats to our existence.
At least, all of those we can now see.

—Excerpted from David Brin’s next novel, Existence, which he hopes readers will see completed in 2010. His previous novels include Earth, The Postman (the basis for the Kevin Costner film of the same name), Foundation’s Triumph, and The Life Eaters (a graphic novel that became an international sensation).

David Brin appears with Jill Tarter, Doug Vakoch, Frank Drake, Ray Kurzweil, Francisco Ayala, and Steven Dick in “Where Are They, All Those Aliens?” the 29th episode in the Closer to Truth: Cosmos, Consciousness, God TV series, hosted and created by Robert Lawrence Kuhn. The series airs Thursdays on the PBS HD network and many other PBS stations. Every Friday, participants will share their views on the previous day’s episode.

From Robert Lawrence Kuhn, host and creator of Closer to Truth:

Down deep, how does the world really work? Science has made spectacular progress assuming that particles and forces describe all that exists. This principle is called “reductionism,” which means that every physical thing can be explained, deep down, in terms of physics. But take ordinary stuff. Study all its parts separately. What do you get? Not what you expect when you see the whole.
What’s going on? Simple ignorance? Or something more? It seems a mystery and it’s called “emergence.” Somehow, the underlying laws of nature— as we know them—cannot account for the world. So can “emergence” explain reality?
Robert Laughlin, a Nobel laureate in physics, rejects the traditional approach that the way to understand the world is to break it down into little pieces. “Let’s imagine you are on an airplane at 40,000 feet, eating peanuts,” Laughlin begins. “You know that the plane won’t disintegrate; that’s why you’re willing to stake your life on it. It’s a law. Now, where did this law come from? Well, you might say, it comes from atoms, but it doesn’t. The reason we know this is because when you want to find out where the rigidity comes from and you take the metal apart in order to do so, the rigidity vanishes away—the same way the meaning of a pointillist painting vanishes away when you get very, very close to it. In other words, rigidity is something that atoms do together. It’s the ‘togetherness’ of atoms that makes the collection rigid. Laws are relationships among measured things that are always true, and they come about because of organization.”
Laughlin stresses that “lots of things in the natural world have this property that you learn less about them by taking them apart. If you want to know whether your airplane is going to come apart, then you look at these big-scale things, these emergent things. Because that is what matters.”
So it depends on what you want to know. This much seems clear. About some things, one learns less about them by taking them apart. The whole is more than the sum of all the parts. But not all scientists think this way.
Peter Atkins, a world-renown chemist and gifted writer at Oxford University, is a tough-minded reductionist who calls claims of emergence “defeatism.” Emergence, he says, can be an excuse for lack of knowledge. He says that “although we scientists might be reductionists who strip matter down to its fundamentals, we’re actually assemblists.” In his view, scientists “try to understand how properties can be explained from simpler components. … When you understand the pieces really well, you understand the whole. … We wouldn’t dream of bringing sociology to bear on understanding the structure of the atom. But in the opposite direction, we could bring the structure of the atom to bear on understanding sociology. … The whole point about science is the driving optimism that it has. You don’t go into science if you don’t think you can find the answers. And as soon as you start saying we’ll never explain that, you’re no longer a scientist in my view. You become a philosopher.”
Either emergence is key. Or emergence is excuse.
Renowned evolutionary biologist Francisco Ayala says that “while living organisms obey the laws of physics and chemistry, the laws of biology are completely different. They transcend, they emerge. … We have to study life processes on their own level.” He draws an analogy to bricks and houses. “You can’t tell an architect that by studying more and more of the laws of bricks that he will understand more and more how to design a house,” Ayala says. “Sometimes people who claim that physics can explain biology, that atoms and molecules can explain organisms, are confused about ontology and epistemology. You have the bricks and you have the house. You remove the bricks, there is no house. In a human being or in any other organism, you remove the atoms and the molecules, nothing’s left. That’s the ontological question.
“Now, if I want to know about houses, I study the work of architects, not of brick-layers,” Ayala continues. “Studying everything about bricks will never explain very much about houses. Each level of organization has its own laws, and meaningful understanding comes only by studying each and every level on its own terms. Similarly, it’s nice to know about the properties of the atoms, the laws of physics and chemistry, but the things I want to know about organisms are completely different things. That’s the epistemological question.”
Going further, can emergence give us clues as to the basic structure, and perhaps deep meaning, of the universe?
Many scientists, understandably, dismiss such a notion. But to Philip Clayton, a philosopher and theologian specializing in science and religion, emergence is a new way of interpreting the world. He somehow sees emergence as a third way between pure science and fundamentalist religion.
According to Clayton, “emergence is the realization that the natural world is composed of multiple levels, and that as systems get more complex, they don’t just continuously evolve into something new, but at some point in complexity a new type of phenomenon appears which needs to be explained in a different way than that of the lower levels.” This is particularly true of organisms, he states.
I pushed Clayton by asking him the following thought question: “Suppose you were God, so to speak, and you knew every possible detail about every possible particle and force, would you still not be able to predict the properties of higher-level phenomena, particularly of organisms?”
“Even God would have to do some looking at the interactions between organism and environment,” Clayton responded. “Organisms are really responsive to their environment, and so even the omniscient scientist, God-qua-scientist, is going to have to look at interactions.”
According to its proponents, emergence may take two forms. Weak emergence is when clumps of material particles attain a certain degree of complexity so that novel properties “appear”—properties unexpected, at least at our state of understanding, which we could not obtain by simply combining the properties of the individual particles. Weak emergence is the kind of emergence we generally find in physics, where the broader system constrains the behavior of the parts (as in the rigidity of metal).
Strong emergence is when whole entities have causal powers that affect all their parts, causal powers that exceed the sum of the powers of all the parts. Strong emergence adds another dimension and is more controversial. In the case of an organism, Clayton says, “it would be silly to say that its behaviors are just a passive constraint and all of the work is done at the chemical level. An organism is an entity that interacts with its environment in the struggle for survival, and that makes it an active agent. Strong emergence then says that this active agent is a causal force which is causing its parts to behave in a particular way.”
Emergence adherents say that what’s operating here is “downward causation”; the organism exercises causal influence on its constituent parts.
The idea of “downward causation” may sound troubling. Can the actions of the sum of the parts, and nothing but these parts, influence in some nontrivial way the parts themselves in some recursive manner? Clayton claims that at each level of organization, we have new information from the empirical world, but he does not “begin with the dogmatic assertion that we’ll be able to tell the whole story top to bottom or bottom to top in one unbroken narrative.”
As I see it, there is something about whole entities that is indeed more than the sum of all their parts, but one must exercise care in describing just exactly what this means. There is no implicit mysticism lurking here. Emergence is a partial description of how the world works, with unique laws operating at each level of reality that are not “reducible” to the laws of the lower levels. Emergence’s claim, disputed by some, is that reductionism does not always work, and even in principle, there will always be cases in which the laws of lower levels cannot explain the properties (or behaviors) of higher levels. Adherents believe that biology, in particular, cannot be explained entirely by physics.
But as for downward causation, I’m still troubled by that.

Robert Lawrence Kuhn speaks with Robert Laughlin, Francis Collins, Francisco Ayala, Charles Harper Jr., Rupert Sheldrake, Peter Atkins, Philip Clayton, and Stephen Wolfram in “How Can Emergence Explain Reality?“ the 28th episode in the Closer to Truth: Cosmos, Consciousness, God TV series, which airs Thursdays on the PBS HD network and many other PBS stations. Every Friday, participants in the series will share their views on the previous day’s episode.