Physics / Book Review

Vol. 5, NO. 2 / May 2020

Until the End of Time: Mind, Matter, and Our Search for Meaning in an Evolving Universe
by Brian Greene
Penguin Random House, 428 pp., $30.00.

Vanity of vanities, saith the Preacher, vanity of vanities; all is vanity.1

Brian Greene has been busy as a bee. Since the publication of The Elegant Universe in 1999, Greene has published The Fabric of the Cosmos, Icarus at the Edge of Time, The Hidden Fabric of Reality, and Incidents of Travel in the Multiverse, and produced a theatrical work, Light Falls.2 Readers have enjoyed his company. And for every good reason. Greene is clever, chatty, accessible. If readers have enjoyed his company, physicists have welcomed his support. They can depend on him. He is a good soldier.

Greene has now published a new book. Until the End of Time is an account of how the universe began and how it might end. Things began with a bang and they will end in a whimper. The second law of thermodynamics prevails. The bang is fine, as generally bangs are, but no one can read about the end times of the universe feeling spiritually refreshed. “As our trek across time will make clear,” Greene writes, “life is likely transient, and all understanding that arose with its emergence will almost certainly dissolve with its conclusion. Nothing is permanent. Nothing is absolute.”3 Given that nothing means anything in the long run, Greene wishes to know what it all means. He is unwilling to say that it does not mean a thing, and unable to say why it does not. The multiverse offers him only its most exiguous consolations.4 On clambering to the edge of space and time, Greene expects to find his double, and so someone exhibiting the same deplorable eagerness to seek relief in travel as Greene himself. It is no wonder that both men are depressed. Greene and that infernal double of his are not alone. So far as the declension of bleakitude goes—bleak, bleaker, take-out, Twitter—they have me at their side, a one-man multitude. At more than four hundred pages, Until the End of Time is very long, and some readers—not me, of course—may feel on reaching its end that they have understood its title in a personal way.

A Foundational Fissure

Greene is a distinguished theoretical physicist, well known for his work on mirror symmetries. The laws of physics are there when he wants them. Whether they are there when he needs them is quite another question. “[B]y fully grasping the behavior of the universe’s fundamental ingredients,” Greene writes, “we tell a rigorous and self-contained story of reality.”5 We do? And rigorous, too? Thermodynamics itself is not obviously derivable either from Newtonian or quantum mechanics, and, if derivable, then not rigorously derivable.6 Never mind. Rigor is just the party line, and party stories are like that. The party’s eschatology remains battle-worthy. “I can envisage a future,” Greene writes, “when scientists will be able to provide a mathematically complete articulation of the fundamental microphysical processes underlying anything that happens, anywhere and anywhen.”7 “Sweet is sweet,” Democritus observed in lines that Greene quotes, “bitter is bitter, hot is hot, cold is cold, color is color; but in truth, there are only atoms and the void.”8

Whatever that far future, in the heat of battle Greene finds himself forced to appeal to the laws of physics and Charles Darwin’s theory of evolution.9 Something like Darwin’s theory is necessary in order to accommodate the facts of life: its existence and emergence, consciousness, language, freedom of the will, religion and religious experience, meaning. This double dependency introduces a fissure into the foundations of Greene’s argument. Darwin’s theory is its own best man, and, as often, its own best friend, but the theory does not follow from any “mathematically complete articulation of the fundamental microphysical processes.” The theory of evolution and the Standard Model of particle physics may both be satisfied in the real world, but Greene requires a scheme in which the theory of evolution emerges inferentially from “the fundamental microphysical processes underlying anything that happens, anywhere and anywhen.” This he does not have. And for the most obvious of reasons. There is no such scheme.10

On those occasions in which Greene does not have the law on his side, he pounds the table. “Make no mistake,” he thunders, “[w]e are [emphasis original] all bags of particles.”11 Whereupon there is an objection. The witness is being led, and by the nose, too. It is one thing to open a bag and see that it contains cookies; quite another, to open a human being and see that it contains a variety of bosons. If no one has performed the requisite experiment, it is because no one knows where to look. Theoretical physics is of no help. Michael Peskin and Daniel Schroeder’s An Introduction to Quantum Field Theory says nothing about human beings, still less about the claim that they are bags of particles.12 The conclusion that Greene affirms appears, if it appears at all, only at the end of a very long inferential chain, one whose links are missing, or incomplete, or conjectural, or badly soldered, or on the point of breaking.

Your witness.

Armies of Unalterable Law

Albert the Great explained the stability of the universe by an appeal to Christian theology. Deus est ubique conservans mundum.13 God is everywhere conserving the world. Although fastidiously disguised, this is an idea that reappears in Until the End of Time, with Greene assigning to the laws of physics the presumptive power of the Holy Ghost. On page 118, Greene remarks that, “everything emerges from the same collection of ingredients, governed [emphasis added] by the same physical principles,” and on page 148, that his “focus is on the existence of laws that govern [emphasis added] your next move.” One paragraph later, they are at it again, those laws, “governing [emphasis added] inanimate collections,”14 and with a little more body English on Greene’s part, “total control” appears within their grasp. The laws of nature are both “immune to all flattery” and “incapable of loosening the reins.”15 A page later still, Schrödinger’s equation is found “deterministically chisel[ing]” its intentions on stone. Imagine what it might chisel if given access to Mount Rushmore.

This is a very old way of thinking, full of an unwholesome allure.16 Philosophers since David Hume have understood that what ought to be the case cannot be derived from what is the case. As much is true for the alethic modalities. An argument to the conclusion that something must happen requires the requisite sense of obligation to be embedded in its premises. Whereupon the laws of nature are again seen barging dramatically into human affairs, unneeded and so unwanted. On tripping—it happens—I can quite well fall toward the center of the earth without their help. The laws of nature do not result in, produce, conduct, convey, control, or otherwise have a hand in human action—or in anything else. They are, those laws, not events; they do not enter into causal relationships; they are no more bound to the wheel of time than the numbers and mathematical functions that they contain. They are, after all, propositions, expressed in ink or hammered into computer code or carried on a woman’s warm breath, a part of the larger linguistic tapestry by which the world is described and explained.

They do what they do. The world is what it is. Nothing is governing anything.

Freedom of the Will

To the extent that he is eager to say that he does not believe in free will, Greene does not believe in free will.17 He is hardly alone. It has become fashionable to say as much. The ensuing renunciation is very often considered a manly kind of purgative, like a round of castor oil or a high colonic. Having been persuaded that he has no say in any matter, Greene feels himself curiously obliged to keep saying so, and is pleased to trace the paternity of the least of his remarks backward to the throat of the Big Bang. If free will does not exist, then arguments about free will are, of course, rather like arguments among billiard balls about which pocket they might join. They cannot help themselves, so the arguments are pointless; but neither can they decide to stop arguing, and so the arguments are endless.

Greene is persuaded that he has seen through all this; he is taken in by no disguise. “Here is a modern version of the argument,” he writes,

that knocks free will back on its heels: Your experiences and mine seem to confirm that we influence the unfolding of reality through actions that reflect our freely willed thoughts, desires, and decisions. Yet, maintaining our physicalist stance, you and I are nothing but constellations of particles whose behavior is fully governed by physical law. Our choices are the result of our particles coursing one way or another through our brains. Our actions are the result of our particles moving this way or that through our bodies. And all particle motion—whether in a brain, a body, or a baseball—is controlled by physics and so is fully dictated by mathematical decree. The equations determine the state of our particles today based on their state yesterday, with no opportunity for any of us to end-run the mathematics and freely shape, or mold, or change the lawful unfolding. Indeed, following this chain ever further back, the big bang is the ultimate source of all particles, and their behavior over cosmic history has been dictated by the nonnegotiable and insensate laws of physics, which determine the structure and function of everything that exists. … We are no more than playthings knocked to and fro by the dispassionate rules of the cosmos18

There is a note of distress in this long paragraph that it would be uncharitable to dismiss. No one wishes to be knocked back, or knocked about, or knocked out, or, God forbid, knocked off.19 It is a paragraph that conveys a kind of fretfulness, as well, for it offers the coldest and meanest kisses at famine prices—those set at the Big Bang. If the distress is earnest, the prices are outrageous, the more so since Greene has gone wrong in calculating them. The great physical theories do not say a word about freedom of the will. Newton’s laws of motion appeal to time, distance, and mass. This is just enough to make a real world rise. Human life is annotated in other terms and by other words: agency and intention, desire and belief, love and hopeless longing—sunt lacrimae rerum et mentem mortalia tangunt.20 Common sense suggests that men act freely when they can, and when they cannot, they do not. This is as far as common sense can go and, for the moment, we have only common sense to go on.

Conflict arises when the discussion turns to theories about theories, theology self-applied, as in the Talmud. If theories in physics are deterministic, does it follow that human freedom does not exist? Greene’s affirmative conclusion is full of the drama of his depression. It is doleful: “We are no more than playthings knocked to and fro by the dispassionate rules of the cosmos.” The sentiment that these words express is hardly new; it owes nothing to modern science. “As flies to wanton boys are we to th’ gods; They kill us for their sport.”21 No one convinced of the existence of freedom of the will is in the least disposed to doubt that the cosmos very often has it in for us. Not me, at any rate. Still, if the cosmos is often at our throat, it is sometimes at our side. Rough justice, I suppose, but Greene needs more than justice, rough or otherwise, to convey his argument, his confidence in its conclusions notwithstanding.

Erwin Schrödinger’s wave equation is a well-posed linear partial differential equation, and, as such, completely deterministic, one state rolling after the other to the end of time. When applied to the quantum world in which various particles brag and bounce, Schrödinger’s wave equation acquires a novel incarnation. Having once been deterministic, it now becomes probabilistic, the Born rule specifying the probability distribution of various experiments. Those probabilities go all the way down. There is no getting rid of them. Nor do they come as much of a surprise. We live amidst the inconvenience and distraction of the real world, and what Greene has to say has long been said before: “I returned, and saw under the sun, that the race is not to the swift, not the battle to the strong, neither yet bread to the wise, nor yet riches to men of understanding, nor yet favor to men of skill; but time and chance happeneth to them all.22

What is a surprise is the strong conclusion that Greene draws from all this. “Much like [Isaac] Newton,” he argues, “Schrödinger leaves no room for free will.”23 No room? Really? Quantum mechanics leaves room enough hospitably to accommodate any number of gabbling philosophers. The place is a polemicist’s paradise. Let me see. An agent is free if he could have done otherwise. Thus Greene. He could have done otherwise, that agent, only if things might have been otherwise. Thus me. The laws of probability uphold the possibility that things might have been otherwise. It is of their essence. A fair coin lands on its face only if it might have landed on its tails. Thus logic. This is not yet a defense of free will. If a man might have done otherwise, it does not follow that he could have done otherwise. Still, it is a step in the right direction. Il n’y a que le premier pas qui coûte.

It hardly helps Greene’s case, or the cause at large, that freedom of the will has forever defied analysis, even in terms that have nothing to do with physics. Never mind what might have been. Is an agent acting freely if and only if he could have done otherwise?24 On making a nuisance of himself by jiggling his feet in a concert hall, a physicist rarely responds to his irritated neighbors—me, for sure—by insisting that he could not help himself. This suggests that he would have stopped jiggling his feet if he could have stopped jiggling them. It is a charitable suggestion. But if he could not do as much, it follows that he would not have done as much, and this does not appear obviously true. He would have stopped jiggling those fat feet of his had I had anything to do with it.


In Greene’s hands, consciousness is, in short order, promoted to the problem of consciousness, and then to the hard problem of consciousness. The problem is hard, Greene believes, because although “I have direct access to my own inner world, I am … at a loss to understand how that world emerges from the motion and interaction of my own [elementary] particles.”25 If Greene is at a loss, David Chalmers is hopelessly flummoxed and has begun companionably contemplating the consciousness of rocks. It is possible that the common English expression dumb as a rock requires revision.26 The idea that I have direct access to my own inner world suggests a distinction between inner and outer worlds.27 The outer world requires indirect access; the inner world is there for the taking. This is hardly the basis for a refined analysis, for it makes a claim that is true only occasionally and only in part. My access to the outer world is often direct, or, at least, as direct as it could possibly be, as when I notice your fist approaching my nose; and my access to the inner world is, as often, indirect, complicated, a matter of hints, hunches, and inference as much as anything else. In Of Human Bondage, Somerset Maugham writes of his protagonist that,

[t]he truth came to him at last. He was in love with her. It was incredible … He tried to think when it had first come to him. He did not know. He only remembered that each time he had gone into the shop, after the first two or three times, it had been with a little feeling in the heart that was pain; and he remembered that when she spoke to him he felt curiously breathless. When she left him it was wretchedness, and when she came to him again it was despair.28

Philip Carey is at a loss in accounting for the history of his own emotions, the odious Mildred appearing in his memory, and in his life, under two quite different systems of interpretation. There is in this nothing unusual. We know what Maugham meant. A man may recognize his emotions only long after the fact, discovering a cold clear core of contempt beneath his insincerely held romantic attachment; he may adjust his judgments and not know whether he is giving up his belief that only the good die young or whether what he really believed was that only the young die good; he may struggle to determine what he is feeling and discover that it is all a hopeless tangle or he may begin in a hopeless tangle and discover under the imperative of action that what he felt, he had felt all along. This is the way things are.

A word appearing is an error in prospect: our access is always indirect. Beyond the words that we use, what other form of access do we have? The gross topological metaphor by which Greene has divided the world into an interior ball of immediate experience surrounded by a remote, barely glimpsed exterior world of public incidents, events, other people, and ever-receding landscapes is absurd. Greene is a sophisticated mathematician, and although there is no assurance that mathematical ideas will prove of relevance in analysis, common sense suggests that they could not hurt. Certain emotions very often seem as if they follow a linear and even a one-dimensional order: nothing, nothing, sentiment, hey! passion, possession, disappointment, discontent, depression, nothing, nothing, zu Asche, zu Staube. Other emotions are otherwise. Quite before assigning to the laws of physics dominance over everything, it would be helpful to have a more refined analysis of the alien territories it is claiming. No one is satisfied with the vocabulary on hand, but no one has a better vocabulary either.

Greene considers the philosopher’s back and forth with engaging respect, but his heart is not in it. The details he is prepared to leave to others. It is the grand metaphysical question that occupies his attention. How do the sentiments, emotions, inclinations, wishes, and desires emerge from a seething mass of elementary particles? Why stop there? How does anything emerge from something? We do not yet understand how gravity emerges from the elementary particles. It seems rather peevish to demand that those particles somehow get together to cobble together something covering the taste of tea. Emergence makes professional sense only against the background of a theory, so that the requisite inference is one that coordinates a theory of the elementary particles and a theory of consciousness. There is no such theory and so no intellectually respectable bridge between mindless particles and mindful experience. If this is so, it is difficult to see why the hard problem of consciousness is hard—or why, for that matter, it is a problem. A problem incapable of solution is not a problem, and if this suggests that the laws of physics might well be incomplete, why should this come as a surprise? They are already incomplete. The spectral-gap problem is undecidable.29 Greene is at a loss when it comes to understanding how any of this is possible. And so are we all.

Under the Astrologer’s Tent

As the ruler of the soul, Ptolemy wrote in the Tetrabiblos, Saturn has the power to make men sordid, petty, mean spirited, indifferent, mean minded, malignant, cowardly, diffident, evil speaking, solitary, fearful, shameless, superstitious, fond of toil, unfeeling, devisors of plots against their friends, gloomy, taking no care of their body.30 We know the type. Some men are just rotten. Brian Greene is under the astrologer’s tent. Ptolemy’s heavy arm is draped in friendship over his own frail shoulder. From Democritus to Steven Weinberg, a great many physicists and philosophers find themselves there. Albert Einstein, too. They disagree about the particulars of planets and particles, but not about the chief thing, the idea that something must account for everything.

The astrologers know perfectly well that everything encompasses a lot. They know, too, that as astrologers, they are obliged to trace a connection in nature between something and everything; a form of force or influence; a tangible, if tentative, line. They have not been reticent. They are full of ideas. Ptolemy appealed to a radiation of sorts proceeding from Saturn, and al-Kindi, writing in the rosy springtime of Islamic philosophy, to stellar rays. Troubled by action at a distance, Albert the Great knew better. A lighthouse in Italy, he remarked, cannot influence a lighthouse in England. Greene has made his appeal; he has pitched his case. The elementary particles are fundamental. They are the something that explains everything. If his own discipline of theoretical physics happens to have a prominence denied Assyriology, he may be forgiven a shiver of satisfaction. But what is the connection between something and everything? It is an obvious question. Beyond saying that the laws of physics govern the elementary particles and everything made of the elementary particles, Greene has nothing more to say and says nothing more about it. No wonder. Greene was born under the sign of Aquarius. We are like that, we Aquarians, taciturn.

It requires a certain coldness to pick all this apart. Nothing in nature is fundamental to everything. If one is doing particle physics, the elementary particles are more fundamental than contracts; in drafting a contract, it is the other way around. Quantum fields are the cynosure of quantum field theory; they do not count in physiology. Philosophers hoped that it would be otherwise and that some set of objects would flaunt proudly their fundamental character, but what is fundamental is inevitably a relative judgment, partial, incomplete, and always changing. If a set of objects is fundamental, it cannot explain everything; if it explains everything, it cannot explain anything.

In the world as it is, there is no relationship in nature answering to causality. Thus al-Ghazālī and thus Hume. Neither is there a relationship in nature between the elementary particles and the world, or worlds, in which they are embedded.31 These metaphysical imputations have all dwindled and disappeared. What remains is a relationship between theories and their models, and not between elementary particles and things—bags or otherwise. Inference is the source of influence, and beyond inference, there is nothing. Is there a relationship in nature that corresponds to the inferential relationship between theories? Not obviously. Hardly ever. To have discovered this is among the great achievements of Western science, but it has come at a price, a profound withdrawal from the world. Under the astrologer’s tent, a sense of gregarious gaiety prevails. Ptolemy’s arm is not yet heavy on Greene’s shoulders; but deep down the astrologers know that the gaiety will not last. The world in which they could cast spells and conjure with action at a distance has disappeared. What remains is the logician’s cold light, cold comfort, I suppose, but better than no comfort at all:

But this rough magic
I here abjure, and, when I have required
Some heavenly music (which even now I do)
To work mine end upon their senses that
This airy charm is for, I’ll break my staff,
Bury it certain fathoms in the earth,
And deeper than did ever plummet sound
I’ll drown my book.


  1. Ecclesiastes 1:2 (King James Version). 
  2. Brian Greene, The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory (New York: W. W. Norton & Company, 1999); Brian Greene, The Fabric of the Cosmos: Space, Time, and the Texture of Reality (New York: Alfred A. Knopf, 2003); Brian Greene, Icarus at the Edge of Time (New York: Alfred A. Knopf, 2008); Brian Greene, The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos (New York: Alfred A. Knopf, 2011); Brian Greene, Incidents of Travel in the Multiverse (London: Hayward Publishing, 2016); Brian Greene, Light Falls: Time, Space, and an Obsession of Einstein, dir. David Horn and Tracy Day, filmed February 19–21, 2019, Gerald W. Lynch Theater, New York, NY, aired May 29, 2019, on PBS, 1:24:40. 
  3. Brian Greene, Until the End of Time: Mind, Matter, and Our Search for Meaning in an Evolving Universe (New York: Penguin Random House, 2020), 16. 
  4. Greene, Until the End of Time, 306–9. One of the advantages of the multiverse is just that it provides an answer of sorts to various fine-tuning questions. Why are the laws of physics what they are or the fundamental constants as they are? In some other universe, they are otherwise. As luck would have it, we live in a universe where the laws of physics are what they are and the fundamental constants are as they are. So far Greene is bound to go in spirit, but on page 307, the conservation of energy is promoted to duty across the multiverse. This might suggest that the fundamental laws of physics are necessary, and so true in all possible worlds. This answers a question that Greene raises on page 52: “Why these laws instead of those?” Were it not for the fact that the laws of physics look nothing like necessary propositions, this would be a very elegant view. It is also a view that would strengthen Greene’s argument against free will. The laws of physics do nothing to prevent a man from acting freely. That is not their business. But they reveal that free action is impossible in the same sense that there is no violating the principle that everything is identical to itself. But this supposes that there is a conflict between the laws of nature and the existence of free will. No one has succeeded in demonstrating the conflict. If I lift my hand, what law of nature do I violate? And yet there is that stubborn difference, as Ludwig Wittgenstein observed, between lifting my hand and the fact that my hand goes up. This is a part of the problem of free will. 
  5. Greene, Until the End of Time, 118. 
  6. If Newtonian mechanics is time-reversible, Josef Loschmidt observed, there is no obvious way in which to derive the second law of thermodynamics from its assumptions. Ludwig Boltzmann’s H-theorem demonstrated that in progressing from a nonequilibrium to an equilibrium state, a physical system must increase in entropy. The argument is fine. Its premises hinge on the assumption of molecular chaos, or Stosszahlansatz, which cannot be derived from Newtonian mechanics itself. If this is so, then neither can the second law of thermodynamics. In this regard, see Jochen Gemmer, Alexander Otte, and Gunter Mahler, “Quantum Approach to a Derivation of the Second Law of ThermodynamicsPhysical Review Letters 86, no. 10 (2001): 1927–30, doi:10.1103/PhysRevLett.86.1927, for references, as well as Barbara Drossel, “On the Relation between the Second Law of Thermodynamics and Classical and Quantum Mechanics” (2014), arxiv:1408.6358. Witness the fearless Drossel: “In the following, I will argue that the second law of thermodynamics cannot be derived from deterministic time-reversible theories such as classical or quantum mechanics.” 
  7. Greene, Until the End of Time, 118. 
  8. Greene, Until the End of Time, 118. 
  9. Greene, Until the End of Time, 9. 
  10. Ernst Mayr remarked that “biological concepts, and the theories based on them, cannot be reduced to the laws and theories of the physical sciences” (Ernst Mayr, “Darwin’s Influence on Modern Thought,” Scientific American, November 24, 2009, 81). The point is obvious. No theory of particle physics makes reference to random variation or natural selection; nor do theories of evolution appeal to quark confinement or the Higgs boson. Alex Rosenberg, a philosopher of science, has been led by this consideration to include the principle of natural selection among the fundamental laws of physics. It is a view that John Dupre modestly described as implausible. See John Dupre, “Is Biology Reducible to the Laws of Physics?American Scientist 95, no. 3 (2007): 276, doi:10.1511/2007.65.276. Chiara Marletto discusses the same questions from the point of view of what she calls constructor theory. See, in particular, her essay, “Life without Design,” Aeon, July 16, 2015. My own point of view, acquired many years ago from Patrick Suppes, my colleague at Stanford in the good old days, is that model theory is the proper discipline in which to express the philosophy of science. See Newton da Costa and Steven French, “The Model-Theoretic Approach in the Philosophy of Science,” Philosophy of Science 57, no. 2 (1990): 248–65, doi:10.1086/289546. There is something that this approach—my approach—never addresses, and that is the mystical nature of the fundamental laws of physics. 
  11. Greene, Until the End of Time, 237. 
  12. Michael Peskin and Daniel Schroeder, An Introduction to Quantum Field Theory (Reading, MA: Westview Press, 1995). 
  13. See Francis Kovach, “The Enduring Question of Action at a Distance in Saint Albert the Great,” Southwestern Journal of Philosophy 10, no. 3 (1979): 161–235, doi:10.5840/swjphil197910356. 
  14. Greene, Until the End of Time, 148. 
  15. Greene, Until the End of Time, 146. 
  16. The point carries over to mathematics. The proposition that two plus two equals four does not, of course, make two plus two equal four. Numbers, like elementary particles, do not answer to our theorems. Nor does the identity between the numbers 2 + 2 and 4 make the proposition that two plus two equals four true. The proposition is true and that is the end of it. Nothing is making anything. 
  17. Greene, Until the End of Time, 146–59. 
  18. Greene, Until the End of Time, 147. There is nothing modern about this argument. 
  19. Let alone knocked up. 
  20. Virgil, Aeneid 1.461ff. Translation by Robert Fagles: “[T]he world is a world of tears and the burdens of mortality touch the heart.” Virgil, The Aeneid, trans. Robert Fagles (New York: Penguin, 2006), 63. 
  21. Shakespeare, King Lear 4.1.35–36. 
  22. Ecclesiastes 9:11 (KJV). 
  23. Greene, Until the End of Time, 149. 
  24. It is not obvious that a man is free to the extent that he could have done otherwise. Here I stand, Martin Luther declared, I can do no other. What judgment about freedom of the will follows? 
  25. Greene, Until the End of Time, 125. 
  26. Greene, Until the End of Time, 132ff. In these pages, Greene describes a number of popular theories about consciousness and information, all of them richly preposterous. 
  27. These issues owe much to Thomas Nagel’s influential paper, “What Is It Like to Be a Bat?Philosophical Review 83, no. 4 (October 1974): 435–50, doi:10.2307/2183914. What is it like to be a bat? One answer is obvious. To be a bat is like being me were I given to squeaking loudly and hanging by my feet. This description might be suitably enlarged to encompass eating insects and navigating by sonar. On the other hand, we might ask what it is like for a bat to be a bat. And the obvious answer is, who knows? But the obvious answer has nothing to do with bats. I can no more imagine what it is like for a bat to be a bat than I can imagine what it is like for anyone but me to be anyone but me. That is a part of the nature of consciousness: to each his own. Nagel concludes that some experiences cannot be described by any proposition; and from this it follows that a physical description of the world must be incomplete. This seems to me a mistake. If what is derived from, a theory is a prediction, it cannot be an experience, and if it is an experience, it cannot be derived from a theory. The same mistake is at work in Frank Jackson’s essay, “What Mary Didn’t Know,” Journal of Philosophy 83, no. 5 (1986): 291–95, doi:10.2307/2026143. What we are left with is the uninspiring conclusion that I cannot have your experiences and vice versa. 
  28. W. Somerset Maughan, Chapter 57, in Of Human Bondage ( and Michael Moncur, 2003–2012), 353, 355. 
  29. See Toby Cubitt, David Perez-Garcia, and Michael Wolf, “Undecidability of the Spectral Gap” (2018), arxiv:1502:04573v3. There are a surprising number of undecidable propositions within mathematical physics—evidence, if any were needed, that undecidability is not simply an oddity of elementary number theory. 
  30. Ptolemy, “On the Qualities of the Soul,” Tetrabiblos III.8. See The Tetrabiblos, ed. Frank Robbins (Cambridge, MA: Harvard University Press, 1980). 
  31. Greene writes often that if A contains B, or is otherwise made up of B-like elements, then the laws that explain B must explain A as well. This is a little like saying that if a bag contains chocolate chip cookies, their recipe must explain something about the bag. In the end, this kind of appeal to the constituents of things represents little more than an attempt to reify the relationship between theories. The requisite diagram does not commute. There is no such relationship in nature. 
  32. William Shakespeare, The Tempest 5.1.47–57. See The Tempest, ed. Virginia Mason Vaughan and Alden Vaughan (London: Methuen Drama, 1999), 266. 

David Berlinski is an American writer.

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