The Big Picture: On the Origins of Life, Meaning and the Universe Itself

Sean Carroll (2016)

In a paragraph

Poetic naturalism considers that our best approach to describing the universe is not a single, unified story told at the fundamental and deterministic level of a quantum wave function, but instead an interconnected series of models appropriate at different levels with emergent descriptions that should be considered real. The evolution of the universe is pushed by increasing entropy and complexity from a low-entropy past. Ethical systems are human constructions that can be improved.

Key points

• Poetic naturalism – there are many ways to talk about the world. Emergent descriptions are real and valid within their domains. We are both collections of atoms and people.Atoms and tables are both real.  So are human experience, choices and values.

• Our best approach to describing the universe is not a single, unified story but an interconnected series of models appropriate at different levels. Each model has a domain in which it is applicable, and the ideas that appear as essential parts of each story have every right to be thought of as “real.” There are many ways of talking about the world. All good ways of talking must be consistent with one another and with the world. Our purposes in the moment determine the best way of talking.

• There is one way of talking about the universe that describes it as elementary particles or quantum states, in which Laplace holds sway and what happens next depends only on the state of the system right now. There is also another way of talking about it, where we zoom out a bit and introduce categories like “people” and “choices.” Although the universe is deterministic, emergent phenomena such as human behaviour are not.

• The case for naturalism has built up gradually over the years and gaps remain. Science does not presume naturalism but has provisionally concluded that naturalism is the best picture of the world we have available.

• Conservation of Momentum: the universe doesn’t need a push; it can just keep going. Conservation of Information: each moment contains precisely the right amount of information to determine every other moment.

• Past Hypothesis of low-entropy state. Our progress through time is pushed from behind, not pulled from ahead. The Arrow of Time.  We remember the past, and our choices affect the future.

• Bayesian updating of credences.

• We have a certain theory of particles and forces, the Core Theory, that seems indisputably accurate within a very wide domain of applicability.

• Poetic naturalism strikes a middle ground, accepting that values are human constructs, but denying that they are therefore illusory or meaningless.

• Strong emergence to strong reductionism. Model shifts with Phase transitions

• One of the most significant features of someone’s ontology is whether or not it includes God. We can use Bayesian reasoning to evaluate features of the world that suggest atheism – eg human life a small feature, no clear miracles or signs, religious variety – or suggest theism – life and consciousness, widespread religious belief. To get a fair view of what theism would naturally predict, we can simply look at what it did predict, before modern astronomy.

• The world is a quantum wave function. For everyday life it is a superposition of configurations of the fermion and boson fields of the Core Theory. The laws of physics underlying everyday life are completely known. There are no psychic powers and no life after death.

• Everett Many-Worlds Interpretation.

• Can the universe simply exist? Yes, it can. What is the best explanation for the existence of the universe? We don’t know.

• Over and over, something that we once thought of as a distinct kind of substance has been revealed to be a particular property of ordinary matter in motion. Life is no different. It is a process rather than a substance.

• It’s not just cups of coffee in which complexity grows and then fades as entropy increases: the universe as a whole does exactly the same thing.

• Life needs compartmentalization, metabolism and replication with variation. We can tell credible stories of how they may have evolved.

• We don’t have reliable ways of judging whether the values of various physical quantities are likely or unlikely. We don’t know that much about whether life would be possible. We might not have just a universe, but a multiverse.  Anthropic principle.

• The best way we have of talking about people and their behaviours makes important reference to their inner mental states; therefore, by the standards of poetic naturalism, those states are real, existing things.

• Ethical systems are invented by human beings, but we can all have productive conversations about how they could be improved, just as we do with all sorts of things that human beings put together.

• Ten Considerations to guide life.

• The universe is much bigger than you or me, and the quest to figure it out unites people with a spectrum of substantive beliefs.

Comments

Carroll sets out a comprehensive understanding of the world based around what he calls “poetic naturalism,” appreciating that we need to use emergent models that we should regard as being “real” in their domains. He also highlights increasing entropy as driving the evolution of the universe and the use of Bayesian reasoning to advance our understanding.  He applies the framework of poetic naturalism to explaining physics, life, consciousness and morality and shows how Bayesian reasoning justifies naturalism and atheism. He combines the approaches of a scientist and of a philosopher and employs the skills of a writer and a teacher. 

NOTES

Prologue

We have two goals in front of us. One is to explain the story of our universe and why we think it’s true, the big picture as we currently understand it.  The other goal is to offer a bit of existential therapy. I want to argue that, though we are part of a universe that runs according to impersonal underlying laws, we nevertheless matter.

It’s not the only way of thinking about what we are. We are collections of atoms, operating independently of any immaterial spirits or influences, and we are thinking and feeling people who bring meaning into existence by the way we live our lives.

Poetic naturalism. “Poetic” reminds us that there is more than one way of talking about the world.

Our best approach to describing the universe is not a single, unified story but an interconnected series of models appropriate at different levels. Each model has a domain in which it is applicable, and the ideas that appear as essential parts of each story have every right to be thought of as “real.”

Poetic naturalism strikes a middle ground, accepting that values are human constructs, but denying that they are therefore illusory or meaningless.

Part One: Cosmos

1. The Fundamental Nature of Reality

As we understand the world better, the idea that it has a transcendent purpose seems increasingly untenable. The old picture has been replaced by a wondrous new one — one that is breathtaking and exhilarating in many ways, challenging and vexing in others. The ground has disappeared beneath us, and we are just beginning to work up the courage to look down.

The broader ontology typically associated with atheism is naturalism.

We will ultimately understand the world as a single, unified reality.

Naturalism presents a hugely grandiose claim, and we have every right to be sceptical. When we look into the eyes of another person, it doesn’t seem like what we’re seeing is simply a collection of atoms, some sort of immensely complicated chemical reaction.

Naturalism isn’t an obvious, default way to think about the world. The case in its favour has built up gradually over the years, a consequence of our relentless quest to improve our understanding of how things work at a deep level, but there is still work to be done. We don’t know how the universe began, or if it’s the only universe. We don’t know the ultimate, complete laws of physics.  We don’t know how life began, or how consciousness arose.

The naturalist needs to make the case that, even without actually having these answers yet, their worldview is still by far the most likely framework in which we will eventually find them.

2. Poetic Naturalism

Should categories like “persons” and “ships” be part of our fundamental ontology at all?  The notion of a ship is a derived category in our ontology, not a fundamental one. It is a useful way of talking about certain subsets of the basic stuff of the universe. We invent the concept of a ship because it is useful to us, not because it’s already there at the deepest level of reality.

Eliminativism.

Our fundamental ontology, the best way we have of talking about the world at the deepest level, is extremely sparse. But many concepts that are part of non-fundamental ways we have of talking about the world — useful ideas describing higher-level, macroscopic reality — deserve to be called “real.”

We refer to such non-useful ways as “wrong” or “false.”

The strategy I’m advocating here can be called poetic naturalism. The poet Muriel Rukeyser once wrote, “The universe is made of stories, not of atoms.” The world is what exists and what happens, but we gain enormous insight by talking about it — telling its story — in different ways.

There are many ways of talking about the world. All good ways of talking must be consistent with one another and with the world.  Our purposes in the moment determine the best way of talking.

Within poetic naturalism we can distinguish among three different kinds of stories we can tell about the world. There is the deepest, most fundamental description we can imagine — the whole universe, exactly described in every microscopic detail. Modern science doesn’t know what that description actually is right now, but we presume that there at least is such an underlying reality. Then there are “emergent” or “effective” descriptions, valid within some limited domain. That’s where we talk about ships and people, macroscopic collections of stuff that we group into individual entities as part of this higher-level vocabulary. Finally, there are values: concepts of right and wrong, purpose and duty, or beauty and ugliness. Unlike higher-level scientific descriptions, these are not determined by the scientific goal of fitting the data. We have other goals: we want to be good people, get along with others, and find meaning in our lives.

The world is just the world, unfolding according to the patterns of nature, free of any judgmental attributes. The world exists; beauty and goodness are things that we bring to it.

Some of the ideas that helped set humanity on the road to naturalism.

3. The World Moves by Itself

Physics is, by far, the simplest science. It doesn’t seem that way, because we know so much about it, and the required knowledge often seems esoteric and technical. But it is blessed by this amazing feature: we can very often make ludicrous simplifications — frictionless surfaces, perfectly spherical bodies — ignoring all manner of ancillary effects, and nevertheless get results that are unreasonably good. For most interesting problems in other sciences, from biology to psychology to economics, if you modelled one tiny aspect of a system while pretending all the others didn’t exist, you would just end up getting nonsense. (Which doesn’t stop people from trying.)

Conservation of momentum. It might not sound like a principle of such dramatic import, but momentum is at the very heart of a shift in how we view the world, from an ancient cosmos of causes and purposes to a modern one of patterns and laws.

The four kinds were material cause, the stuff of which an object is made; formal cause, the essential property that makes an object what it is; efficient cause, the thing that brings the object about (closest to our informal notion of “cause”); and final cause, the purpose for which an object exists.  For Aristotle, physics was a story of natures and causes.

The universe doesn’t need a push; it can just keep going.

4. What Determines What Will Happen?

Pierre-Simon Laplace.  On God: “I had no need of that hypothesis.”  Laplace was one of the first thinkers to truly understand classical (Newtonian) mechanics, deep in his bones — better than Newton himself. Newtonian gravity could be thought of as a field theory.

He realized that there was a simple answer to the question “What determines what will happen next?” And the answer is “The state of the universe right now.”

When we talk about simple Newtonian systems, like the planets moving through the solar system, determinism is part of the picture. When we talk about enormously more complex things like people, there’s no way for us to have enough information to make ironclad predictions. Our best theories of people, presented on their own terms and without reference to underlying particles and forces, leave plenty of room for human choice.

The universe is resolutely focused on the current moment; it marches forward, instant to instant, under the grip of unbreakable physical laws, with no heed paid to its glorious accomplishments or to its hopeful prospects.  Laplace’s Demon.

By the “state” of the universe, or any subsystem thereof, we mean the position and the velocity of every particle within it.  We can use the laws of physics to integrate forward (or backward) and get the state of the universe at any other time.

Conservation of information implies that each moment contains precisely the right amount of information to determine every other moment. To simulate the entire universe with good accuracy, you basically have to be the universe.

Chaos theory says that slightly imperfect information leads to very imperfect prediction.

There is one way of talking about the universe that describes it as elementary particles or quantum states, in which Laplace holds sway and what happens next depends only on the state of the system right now. There is also another way of talking about it, where we zoom out a bit and introduce categories like “ people ” and “ choices . ” Unlike our best theory of planets or pendulums, our best theories of human behaviour are not deterministic.

5. Reasons Why

Abduction, or “inference to the best explanation.”

The “reasons” and “causes” why things happen, in other words, aren’t fundamental; they are emergent.

The secret here is to accept that such questions may or may not have answers.

6. Our Universe

It’s not surprising that ancient cosmologists, when theorizing about the universe, took as its fulcrum the thing they understood the best: themselves.

The Big Bang doesn’t actually mark the beginning of our universe; it marks the end of our theoretical understanding.

7. Time’s Arrow

It’s been popular to imagine that the world is teleological — directed toward some future goal. But it’s better to think of it as pushed from a start.

Physical motions, to the best of our understanding, are reversible. Both directions of time are on an equal footing.

Boltzmann. Identify the entropy of a system with the number of different states that would be macroscopically indistinguishable from the state it is actually in. Technically, it’s the logarithm of the number of indistinguishable states.

In equilibrium, time has no arrow.

Earlier very low-entropy state.  Past Hypothesis.  Nobody knows exactly why the early universe had such a low entropy. It’s one of those features of our world that may have a deeper explanation we haven’t yet found, or may just be a true fact we need to learn to accept.

8. Memories and Causes

Our progress through time is pushed from behind, not pulled from ahead.

Part Two: Understanding

9. Learning about the World

Frequentists v Bayesians

Credences. Prior credences.

10. Updating Our Knowledge

If we think our opponent would draw precisely one card only 10 percent of the time if they had a pair, we remove nine-tenths of the grains of sand from the jar labelled “pair”

The absence of consistency across sacred texts counts as evidence against theism.

Bayes’s Theorem is one of those insights that can change the way we go through life.

11. Is It Okay to Doubt Everything?

“Boltzmann Brain”

Set our prior credence in radically sceptical scenarios at very low values.

If we take the world roughly at face value, we have a way of moving forward.

12. Reality Emerges

There are many ways of talking about the world, each of which captures a different aspect of the underlying whole.

The classic example of emergence, one you should constantly return to whenever these things get confusing, involves the air in the room around you.

The different stories or theories use utterly different vocabularies; they are different ontologies, despite describing the same underlying reality.  Each theory has a particular domain of applicability. Within their respective domains of applicability, each theory is autonomous. If we have two different theories that both accurately describe the same underlying reality, they must be related to each other and mutually consistent.

We often call the first theory the “microscopic” or “fine-grained” or “fundamental” one, and the second the “macroscopic” or “coarse-grained” or “emergent” or “effective” one.

Trade-off between comprehensiveness of a theory and its practicality.

Air is unusually simple. All we’re really doing to derive the fluid description is calculating the average properties of all the molecules. Quantum mechanics, in particular, features the phenomenon of entanglement.

Space itself may be emergent rather than fundamental.

Phase transitions.

13. What Exists, and What Is Illusion?

Strong emergence: the behaviour of a system with many parts is not reducible to the aggregate behaviour of all those parts, even in principle.

Range from “strong emergence” (all stories are autonomous, even incompatible) on one end and “strong reductionism” (all stories reduce to one fundamental one) on the other.

Eliminativism.

Atoms are real; tables are real.

“model-dependent realism.”

How poetic naturalism divides up “fundamental” versus “emergent / effective,” “real” versus “illusion,” and “objective” versus “subjective.”

14. Planets of Belief

Whole systems of belief fit together with one another, in more or less comfortable ways, pulled in by a mutual epistemological force.

Self-serving bias. Confirmation bias

15. Accepting Uncertainty

The number X that we obtain by multiplying together all of the primes from our list, exactly once each, and adding 1 to the result. Then X is clearly larger than any of the primes in our list. But it is not divisible by any of them, since dividing by any of them yields a remainder.

It’s a good thing that credences never reach these points of absolute certainty; if they did, no amount of new evidence could ever change our minds.

We want to avoid being sucked into a black hole of belief, where our convictions are so strong that we can never escape, no matter what kind of new insight or information we obtain.

Useful to distinguish between “knowing” and “knowing with absolute logical certainty” If our credence for some proposition is 0.0000000001, we’re not absolutely certain it’s wrong — but it’s okay to proceed as if we know it is.

16. What Can We Know about the World without Actually Looking at It?

St Martin-in-the-Fields.  Transcendent.

Methodological naturalism. Methodological empiricism.  Not that science presumes naturalism; it’s that science has provisionally concluded that naturalism is the best picture of the world we have available.  We find that naturalism gives the best account of the evidence we have.

17. Who Am I?

Most people are essentialists about gender, but things are changing.

Poetic naturalism sees things differently. Categories such as “male” and “female” are human inventions — stories we tell because it helps us make sense of our world. The basic stuff of reality is a quantum wave function, or a collection of particles and forces — whatever the fundamental stuff turns out to be. Everything else is an overlay, a vocabulary created by us for particular purposes.

Whether a particular way of talking about the world is useful. And usefulness is always relative to some purpose. If we’re being scientists, our goal is to describe and understand what happens in the world, and “useful” means “providing an accurate model of some aspect of reality.” If we’re interested in a person’s health, “useful” might mean “helping us see how to make a person more healthy.”

18. Abducting God

One of the most significant features of someone’s ontology is whether or not it includes God. It’s the biggest part of the big picture.

If the likelihood of no evil is larger under theism, then the likelihood of evil is larger under atheism, so evil’s existence increases our credence that atheism is correct.

It’s easy to come up with features of our universe that provide evidence for atheism over theism. Imagine a world in which miracles happened frequently, rather than rarely or not at all. Imagine a world in which all of the religious traditions from around the globe independently came up with precisely the same doctrines and stories about God. Imagine a universe that was relatively small, with just the sun and moon and Earth, no other stars or galaxies. Imagine a world in which religious texts consistently provided specific, true, nonintuitive pieces of scientific information. Imagine a world in which human beings were completely separate from the rest of biological history. Imagine a world in which souls survived after death, and frequently visited and interacted with the world of the living, telling compelling stories of life in heaven. Imagine a world that was free of random suffering. Imagine a world that was perfectly just, in which the relative state of happiness of each person was precisely proportional to their virtue. In any of those worlds, diligent seekers of true ontology would quite rightly take those aspects of reality as evidence for God’s existence. It follows, as the night the day, that the absence of these features is evidence in favour of atheism.

The simple fact that people think about God counts as some evidence that he is real.  Imagine a world with physical matter, but in which life never arose. Or a universe with life, but no consciousness.  Or a universe with conscious beings, but ones who found no joy or meaning in their existence. At first glance, the likelihoods of such versions of reality would seem to be higher under atheism than under theism. Much of the task of the rest of this book is to describe how these features are quite likely in a naturalistic worldview.

I would rather live in a universe where I am responsible for creating my own values and living up to them the best I can, than in a universe in which God hands them down, and does so in an infuriatingly vague way. This preference might unconsciously bias me against theism. On the other hand, I’m not at all happy that my life will come to an end relatively soon (cosmically speaking), with no hope for continuing on; so that might bias me toward it.

Part Three: Essence

19. How Much We Know

We have a certain theory of particles and forces, the Core Theory, that seems indisputably accurate within a very wide domain of applicability.

The Core Theory, and the framework of quantum field theory on which it is based — are enough to tell us that there are no psychic powers.

20. The Quantum Realm

In quantum mechanics, the state of a system is a superposition of all the possible measurement outcomes, known as the “wave function” of the system.  The “wave function of the universe.”

Everett.  Many-Worlds Interpretation.

22. The Core Theory

Both particles and forces arise out of fields.  Quantum field theory. Standard model of particle physics. General relativity.

“What the world is” is a quantum wave function. A wave function is a superposition of configurations of stuff. The next question is “What is the stuff that the wave function is a function of?” The answer, as far as the regime of our everyday life is concerned, is “the fermion and boson fields of the Core Theory.” The laws of physics underlying everyday life are completely known.

23. The Stuff of Which We Are Made

Crossing symmetry. Feynman diagrams. Dark-matter particle.

We have a complete inventory of the particles and forces and interactions that are strong enough to have any noticeable effect on anything.

24. The Effective Theory of the Everyday World

Effective theories. The emergent phenomena we see in our everyday lives do not depend on dark matter or other new physics. Moreover, they only depend on underlying reality through their dependence on the Core Theory particles and interactions.

Some small loopholes in our arguments that the laws of physics underlying everyday life are completely known.

The most likely scenario for future progress is that the Core Theory continues to serve as an extremely good model in its domain of applicability while we push forward to understand the world better at the levels above, below, and to the side.

25. Why Does the Universe Exist?

Could the universe, possibly, simply exist?

What is the best explanation for the existence of the universe?

In classical general relativity, the Big Bang is the beginning of spacetime; in quantum general relativity — whatever that may be, since nobody has a complete formulation of such a theory as yet — we don’t know whether the universe has a beginning or not.

Stephen Hawking and James Hartle back in the early 1980s, when they helped pioneer the subject of “quantum cosmology.” They showed how to construct a quantum state of the universe in which time isn’t truly fundamental, and in which the Big Bang represents the beginning of time as we know it.

Talking about “causes” is not the right vocabulary to use when thinking about how the universe works at a deep level. We need to be asking ourselves not whether the universe had a cause but whether having a first moment in time is compatible with the laws of nature.

Every conserved quantity characterizing the universe (energy, momentum, charge) is exactly zero.  The energy of “stuff” like matter and radiation is positive, but the energy associated with the gravitational field (the curvature of spacetime is negative, and exactly enough to cancel the positive energy in the stuff.

Move from the first question, “Can the universe simply exist?” (yes, it can) to the second, harder one: “What is the best explanation for the existence of the universe?” The answer is certainly “We don’t know.”

26. Body and Soul

Princess Elisabeth of Bohemia

27. Death Is the End

Life as a process rather than a substance.

Over and over, something that we once thought of as a distinct kind of substance has been revealed to be a particular property of ordinary matter in motion. Life is no different.

Contradict the laws of physics

Part Four: Complexity

28. The Universe in a Cup of Coffee

William Paley

Immanuel Kant, writing in 1784, mused, “There will never be a Newton for the blade of grass.”

Complexity first goes up, then goes down. It’s not just cups of coffee in which complexity grows and then fades as entropy increases: the universe as a whole does exactly the same thing.

“Fractal” and “complex”

Caused by effects that stretch over long distances.

Our goal is to offer a plausibility sketch that the world can ultimately be understood on the basis of naturalism. We don’t know how life began, or how consciousness works, but we can argue that there’s little or no reason to look beyond the natural world for the right explanations.

Asking that our understanding of human life be compatible with what we know about the underlying physics places some interesting constraints on what life is and how it operates. Conclude with very high confidence that individual lives are finite in scope.

Those swirls in the cream mixing into the coffee? That’s us. Ephemeral patterns of complexity, riding a wave of increasing entropy from simple beginnings to a simple end.

29. Light and Life

There is not a single agreed-upon definition that clearly separates things that are “alive” from those that are not.

From the sun is energy with very low entropy — so-called free energy, or better “useful energy”

One way of formulating the second law is to say that, in an isolated system, free energy is converted into disordered energy as time passes.

Whether a certain amount of energy is “free” or “disordered” depends on its environment

The sun is a hot spot in a cold sky.

30. Funnelling Energy

The basic power battery of life here on Earth is a molecule called adenosine triphosphate, or ATP, which switches to adenosine diphosphate (ADP).

Molecular storm within cell.

31. Spontaneous Organization

Life needs compartmentalization, metabolism and replication with variation.

Lipids have a “head” that is hydrophilic (attracted to water) on one end, and a “tail” that is hydrophobic (repelled by water). Lipids include fatty acids, which are relatively simple, and phospholipids.  Cellular membranes in organisms living on Earth today are made from bilayers of phospholipids.

Bayesian reasoning, emergence, the second law — come together to help explain the appearance of complex structures in a world governed by simple, unguided laws of nature.

32. The Origin and Purpose of Life

Alkaline vents.

The relationship of RNA to DNA is like the relationship of an oral tradition of poetry to words written down in books.

We’ve made amazing progress in understanding what life is and how it came to be, and there’s every reason to think that progress will continue until we have figured it out. The work ahead will involve chemistry, physics, mathematics, and biology, not magic.

33. Evolution’s Bootstraps

Lenski.  E. coli evolve over many generations, such as to metabolize citrate.

“There is grandeur in this view of life,” Darwin writes in On the Origin of Species.

34. Searching through the Landscape

Natural selection can be thought of as a search algorithm. Evolution searches through the fitness landscape, looking for higher peaks. Genetic algorithms.

Not only can eyes be developed in stages of increasing complexity and fitness, but we actually see such development in real creatures alive today. And the human eye, as wondrous as it is, has unambiguous flaws that would be inexcusable for a talented designer but make perfect sense in light of evolution.

35. Emergent Purpose

As time passes and entropy increases, the configuration of matter in the universe takes on different forms, enabling the emergence of different higher-level ways of talking. The appearance of something like “purpose” simply comes down to the question “Is ‘purpose’ a useful concept when developing an effective theory of this part of reality in this particular domain of applicability?”

The fact that information is an effective way of characterizing certain physical realities is a true and nontrivial insight onto the world.

When we talk about the information contained in the book you are currently reading, what we mean is that these words are correlated with certain ideas.

It is unclear why God would place such a high value on acting in ways that human beings can’t notice. This approach reduces theism to the case of the angel steering the moon, which we considered in chapter 10. You can’t disprove the theory by any possible experiment, since it is designed precisely to be indistinguishable from ordinary physical evolution. But it doesn’t gain you anything either. It makes the most sense to place our credence in the idea that the divine influences simply aren’t there.

36. Are We the Point?

In Bayesian language, the likelihood of life appearing in the universe might be large under theism, and small under naturalism. We can therefore conclude that our very existence is strong evidence in favour of God. The most important step is to determine the probability that we would measure various experimental outcomes under each theory. Easier said than done, given that there are many specific versions of both theism and naturalism.

If naturalism is true, what is the probability that the universe would be able to support life?  The usual fine-tuning argument is that the probability is very small, because small changes in the numbers that define our world would render life impossible.

Cosmological constant.

Stars run by nuclear fusion. The first step is when two protons come together and one of them converts to a neutron, creating a nucleus of deuterium. If the neutron were a little bit heavier, that reaction would not occur in stars. If it were a little bit lighter, all of the hydrogen in the early universe would have been converted to helium.

We don’t have reliable ways of judging whether the values of various physical quantities are likely or unlikely.  We don’t know that much about whether life would be possible.

We might not have just a universe, but a multiverse. The physical numbers that are purportedly fine-tuned — even supposedly fixed constants, such as the mass of the neutron — could take on very different values from place to place.

Anthropic principle

Cosmological multiverse.

Every one of those ways to hide the extra dimensions — what string theorists call a compactification — leads to an effective theory with different observable laws of physics.

In any particular region, inflation will eventually end — and when it does we can find ourselves with a completely different compactification.

If the eventual appearance of life were an important consideration for God when he was designing the universe, it is hard to understand why life seems so unimportant in the final product. 

To get a more fair view of what theism would naturally predict, we can simply look at what it did predict, before we made modern astronomical observations.

Part Five: Thinking

37. Crawling into Consciousness

Human beings are part and parcel of the natural world, thoughts and emotions and all.

There does seem to be a kind of prime minister of the parliament, a seat of cognition where the inputs from many modules are sewn together into a continuum of consciousness.

The ability to take time to contemplate multiple alternatives, breaking the immediate connection between stimulus and response — started to become selected for by evolution once we crawled up onto the rocks.

Our imaginative faculties grew out of the evolutionary pressure in favour of developing the ability to weigh competing options for our future actions.

Semantic memory and episodic memory. Episodic memory and imagination engage the same neural machinery.  When we remember a past event, the brain pulls out the script and puts on a little performance of the sights and sounds and smells.

38. The Babbling Brain

MEG machine: magneto-encephalography. These probes attached to my skull could sense me thinking. What we call a “thought” corresponds directly and unmistakably to the motion of certain charged particles inside my head.

It’s not the neurons themselves that encode information but the way they are connected to one another.

The network structure of the brain, known as its connectome. Small-world network.

39. What Thinks?

Turing test. Chinese Room. Substrate independence.

There is something going on inside the person’s head, and we had better take it into account if we want to correctly predict how they will behave. Intentional stance.

Theory of mind.  It is helpful to have models of the world around you, including other organisms and their models.

40. The Hard Problem

Mind-body problem: how can we hope to account for mental reality using only physical concepts? 

The Easy Problems are about functioning; the Hard Problem is about experiencing. The Easy Problem (which is hard), and the Hard Problem (which is impossible).

There are a number of thought experiments that try to illustrate how hard the Hard Problem really is. A famous one is Mary the Colour Scientist.

41. Zombies and Stories

Philosophical zombie.

A naturalist but not a physicalist — we can accept that there is only the natural world, but believe that there is more to it than its physical properties.

The physical things with which we are familiar can have other kinds of properties — there can be a separate category of mental properties. This view is property dualism, as distinct from good old-fashioned Cartesian substance dualism.

As long as zombies are conceivable or logically possible, Chalmers argues, then we know that consciousness is not purely physical.  Why do zombies lie all the time?

There is a part of the universe I choose to call “me.”

“I am experiencing redness.” This is a useful thing to say.  Therefore the “experience of redness” is a real thing .

The best way we have of talking about people and their behaviours makes important reference to their inner mental states; therefore, by the standards of poetic naturalism, those states are real, existing things.

42. Are Photons Conscious?

The appearance of consciousness is a phase transition. We simply don’t gain anything by attributing the features of consciousness to individual particles.

Some things just come into being as the universe evolves and entropy and complexity grow: galaxies, planets, organisms, consciousness.

Consciousness is confusing, and quantum mechanics is confusing  so maybe they’re somehow related.

43. What Acts on What?

We live in a reality that can be fruitfully talked about in many different ways.  We have an extravagant assortment of theories, models, vocabularies, stories.

The trap of using multiple vocabularies at the same time.

Causal closure of the physical.

Poetic naturalists tend to view downward causation as a deeply misguided idea. The individual molecule has no idea it’s part of a snowflake, and could not care less.

44. Freedom to Choose

There’s a sense in which you do have free will. There’s also a sense in which you don’t.

The concept of choice does exist, and it would be difficult indeed to describe human beings without it.

Either vocabulary is perfectly legitimate, but mixing them leads to nonsense.

We remember the past, and our choices affect the future. Laplace’s Demon discerns no such imbalance; he sees the whole history of the world with perfect clarity.

The unavoidable reality of our incomplete knowledge is responsible for why we find it useful to talk about the future using a language of choice and causation.

Some formulations of “free will” go well beyond anything that a poetic naturalist would be willing to countenance. There is what is called libertarian freedom.

Libet.

Base our ideas about personal responsibility on the best possible understanding of how the brain works that we can possibly achieve, and be willing to update those ideas.

Part Six: Caring

45. Three Billion Heartbeats

Carl Sagan reflections by wife Ann Druyan: Every single moment that we were alive and we were together was miraculous — not miraculous in the sense of inexplicable or supernatural. We knew we were beneficiaries of chance … . That pure chance could be so generous and so kind … . That we could find each other.

Three billion heartbeats in a life.

Our folk ontology treats meaning as something wholly different from the physical stuff of the world. It might be given by God, or inherent in life’s spiritual dimension, or part of a teleological inclination built into the universe itself, or part of an ineffable, transcendent aspect of reality. Poetic naturalism rejects all of those possibilities, and asks us to take the dramatic step of viewing meaning in the same way we view other concepts that human beings invent to talk about the universe.

Poetic naturalism offers no such escape from the demands of meeting life in a creative and individual way. It is about you: it’s up to you, me, and every other person to create meaning and purpose for ourselves.

Consciousness means that what we care about, and how we behave in response to those impulses, can change over time as a result of our learning, our interaction with others, and our own self-reflection. Our instincts and unreflective desires aren’t all we have; they’re just a starting point for building something significant.

46. What Is and What Ought to Be

“You can’t derive ought from is.”

Searle is relying on a hidden premise

Instrumental rationality.

47. Rules and Consequences

The descendant of Abraham’s dilemma in our secularized, technological world is something called the trolley problem.

Yet we must live and act.

We are also human beings who make choices and care about what happens to ourselves and to others. What’s the best way to think about how we should live?

Our ethical systems are things that are constructed by us human beings, not discovered out there in the world , and should be evaluated accordingly .

Joshua Greene, we not only have “thinking fast and slow”; we also have “morality fast and slow.”  The unruly parliament that constitutes our brain includes both deontological and consequentialist factions.

Morality adds an evaluative component to how we talk about the world. A moral framework is “useful” to a poetic naturalist to the extent that it reflects and systematizes our moral commitments in a logically coherent way.

Ethical systems are invented by human beings, but we can all have productive conversations about how they could be improved, just as we do with all sorts of things that human beings put together.

Philosopher Sharon Street distinguishes between Kantian constructivism, after Immanuel Kant, and Humean constructivism, after David Hume.  A Humean constructivist takes one more step: morality is constructed, and different people might very well construct different moral frameworks for themselves.

48. Constructing Goodness

Utilitarianism doesn’t always do a good job of embodying our moral sentiments.

“soft consequentialism”

Our values have not yet caught up to our best ontology.

49. Listening to the World

The idea of “Ten Commandments” is a deeply compelling one. It combines two impulses that are ingrained in our nature as human beings: making lists of ten things, and telling other people how to behave.

Ten Considerations:

1 . Life Isn’t Forever.

2 . Desire Is Built into Life.

3 . What Matters Is What Matters to People.

4 . We Can Always Do Better.

5 . It Pays to Listen.

6 . There Is No Natural Way to Be.

7 . It Takes All Kinds.

8 . The Universe Is in Our Hands.

9 . We Can Do Better Than Happiness. Synchronic meaning and diachronic meaning. At the end of the day, or the end of your life, it doesn’t matter so much that you were happy much of the time. Wouldn’t you rather have a good story to tell?

10 . Reality Guides Us.

50. Existential Therapy

“The Only Way,” from the Emerson, Lake & Palmer album Tarkus.

Awe has connotations of reverence: “this fills me with awe and I am not worthy.” Wonder has connotations of curiosity: “this fills me with wonder and I am going to figure it out.” I will take wonder over awe every day.

I always thought it was crucial that different aspects of the world fit together and make sense. Everything we’ve experienced about the universe suggests that it is intelligible: if we try hard enough we can come to understand it.

The important distinction is not between theists and naturalists; it’s between people who care enough about the universe to make a good-faith effort to understand it, and those who fit it into a predetermined box or simply take it for granted. The universe is much bigger than you or me, and the quest to figure it out unites people with a spectrum of substantive beliefs.

An abiding joy in puzzling out the nature of reality.

Appendix: The Equation Underlying You and Me

The Feynman path integral for the Core Theory.

Fermions and bosons.

The Core Theory underlying our everyday lives is extremely precise, rigid, and well defined.