Why Does the World Exist?: An Existential Detective Story (11 page)

But maybe he was undervaluing the power of simplicity. For scientists, after all, simplicity is nothing less than a guide to truth. As the physicist Richard Feynman put it, “
The truth always
turns out to be simpler than you thought.” It is not that they want
reality
to be simple; rather, they want their
theories
of reality to be as simple as possible.

It’s surprisingly tricky to say what makes one theory simpler than another. Still, there are some agreed-upon criteria. Simple theories posit few entities, and few
kinds
of entity; they obey the principle of Occam’s razor: “do not multiply entities needlessly.” Simple theories also have the minimum number of laws, and those laws take the simplest mathematical form. (Straight-line equations, for example, are deemed to be simpler than complicated curves.) Simple theories are also parsimonious when it comes to arbitrary features—unexplained numbers like Planck’s constant and the speed of light.

Simple theories are obviously more convenient to use, more congenial to our intellects. They also appeal to our aesthetic sense. But why should they be more likely to be
true
than complex theories? This is a question that philosophers of science have never satisfactorily answered. “I suspect that it is not possible fully to justify the idea that simple theories are objectively more likely to be true than are complex ones,” Jack Smart has observed. Nevertheless, when scientists have in hand two rival theories that are equally consistent with past evidence, it is the simpler of the two that they invariably prefer, since it is seen as more likely to be confirmed by future data. And the conviction that simpler theories are more probable than complicated ones is not confined to scientists.
Suppose you have two equally well-confirmed theories
, A and B. Theory A predicts that all life in the Southern Hemisphere will be wiped out tomorrow. Theory B predicts that all life in the Northern Hemisphere will be wiped out tomorrow. And suppose that Theory A is very complicated and Theory B is very simple. Then which of us northerners would not be trying to get on a plane for the Southern Hemisphere tonight?

If simple theories are indeed more likely to be true than complicated ones, that must be because the world as a whole has a deep-seated bias toward simplicity. Such a bias seems to have been successfully exploited by physicists in their search for the ultimate laws of nature. The “symmetries” that physicists look for in those laws are, as the Nobel laureate Steven Weinberg has pointed out, really principles of simplicity—principles that say, for example, the future should resemble the past in its most basic respects.

But simplicity is, for scientists, more than a guide to truth. It is also, as Weinberg has observed, “
part of what we mean
by an explanation.” It is simplicity that distinguishes a “beautiful explanatory theory” in physics from a “mere list of data.” Richard Dawkins made a similar point. Complicated realities, Dawkins submits, are more improbable than simple ones, and therefore stand in greater need of explanation. Take the existence of biological life. To posit a God as its cause is a nonstarter, Dawkins argues, since “
any God capable
of designing a universe, carefully and foresightfully tuned to lead to our evolution, must be a supremely complex and improbable entity who needs an even bigger explanation than the one he is supposed to provide.” It is the simplicity of natural selection that makes it a satisfying explanation of life.

Now, the simplest theory of all is the one that says NOTHING EXISTS. This theory—the Theory of Nothingness—posits no laws and no entities; it has zero arbitrary features. If simplicity is indeed a mark of truth, then the Theory of Nothingness must enjoy the highest
a priori
probability. Absent any data about reality, the Null World is the one that should be expected to obtain. But it does not obtain! There is evidently a great abundance of Being. If we are scientifically minded, this should surprise us—shouldn’t it?

Yet it did not surprise Grünbaum. So what, he said, if the Null World has the greatest
a priori
probability? “Probabilities just do not legislate ontologically,” he kept insisting. Probability is not, in other words, a force driving the way reality should turn out, a force that had to be countered by
another
force, divine or otherwise, if there was to be Something rather than Nothing. That the universe seemed to confound the canons of science just didn’t strike him as an intellectual problem.

Sometimes, of course, complicated theories do turn out to be true. As Grünbaum had pointed out, the modern theory of chemistry, which posits a whole periodic table full of elements, is a lot more complicated than the ancient chemical theory of Thales, based on water alone. But when scientists are faced with such complicated theories, they invariably look for simpler ones that underlie and explain them. A notable case is the contemporary quest for a unified theory of physics. Here the motive is to show that the four basic forces of physics—gravity, electromagnetism, the strong nuclear force, and the weak nuclear force—are all manifestations of a single underlying superforce. Such a unified theory—a “Theory of Everything,” as it is sometimes called—would be superior to the partial theories it supersedes because of its relative simplicity. Instead of positing four forces, each governed by a distinct law, it would posit a single force-
cum
-law. In doing so, it would offer a more comprehensive explanation of nature than the current theoretical patchwork. Indeed, such a unified theory might turn out to be the closest we can come to giving a complete physical explanation of why the world is the way it is. But the final theory of physics would still leave a residue of mystery—why
this
force, why
this
law? It would not contain within itself an answer to the question of
why
it was the final theory. So it would not live up to the principle that every fact must have an explanation—the Principle of Sufficient Reason.

On the face of it, the only theory that does obey this principle is the Theory of Nothingness. That is why it’s surprising that the Theory of Nothingness turns out to be false, that there is a world of Something. And any theory of this world of Something, however simple and ultimate, is doomed to fail the test of Sufficient Reason.

Or is it? Mightn’t there be, after all, a theory of this world that leaves no unexplained explainers, one that reduces the residue of mystery all the way to zero? Finding such a theory would be tantamount to answering the question
Why is there something rather than nothing?
Adolf Grünbaum and his ilk might think this theory is not worth searching for—especially if the search takes a supernatural turn. But their arguments, while admittedly formidable, did not leave me convinced that the quest should be abandoned. There is nothing I dislike more than premature intellectual closure.

THAT NIGHT I
got a personal glimpse into the Abyss of Nonbeing.

The plan for the evening seemed a good one. Adolf, accompanied by his wife Thelma, would pick me up at my hotel. Then we would set off for dinner at a restaurant called Le Mont, perched high above Pittsburgh on Mount Washington. The view was reputedly spectacular.

Adolf was driving a late-model Mercedes-Benz. His wife, a charming and somewhat abstracted woman of the same age, sat next to him. I sat, like their son, in the back seat.

It was when we got onto the freeway running along the Allegheny River that my pulse began to race. A diminutive man, shrunken by age, Adolf could barely see above the dashboard. It was like having, well, Mr. Magoo for a chauffeur. Oblivious to the heavy and fast-moving traffic around us, he maintained a constant monologue as he tried to work out the route. We were having one close call after another, but Adolf and his wife seemed blissfully unaware of the angry honks coming from the other cars. The longer we drove, the more Mount Washington seemed to recede from us. It was like a cruel real-life version of Zeno’s paradox.

Eventually we somehow found ourselves on the
other
side of the mountain—where, perversely, the speed and volume of the traffic only increased. The angry honking around us continued, and the probability of escaping a serious collision seemed headed toward zero. Would I walk away from the smoking wreckage? Possibly: we were, after all, in a late-model Mercedes. But I couldn’t help fearing that the precious flame of my consciousness was about to be extinguished eternally, that I was in danger of making the transition from Pittsburgh to Nothingness.

Finally Adolf responded to my frantic pleas to pull over with a breathtaking maneuver: he came to a dead stop in the middle lane. A passing state trooper took note of our predicament, and we were kindly set right and escorted to the mountaintop restaurant. On arriving, I found myself to be more than usually in need of a fortifying bumper of champagne.

“Go relax and enjoy yourself! Don’t worry about why there’s a world—it’s an ill-conceived question!” Grünbaum exclaimed to me nonchalantly, with a trace of paternal affection, once the three of us had been seated at our table. The view was indeed stunning. All of Pittsburgh lay spread out below us. I could see where the Allegheny and the Monongahela came together to form the Ohio River. Bridges, festooned with twinkling lights, spanned the waters every which way.

The restaurant itself had a curiously 1950s feel to it, with older waiters in black tie, like extras in a Marx Brothers movie, and lots of crystal and brocade everywhere. Across the room, a local torch singer in sequins, accompanied by a pianist, belted out “At the Copa.”

As I listened to my distinguished interlocutor above the music—“They need
p
and
q
, these boys, they need
p
and
q
!” he exclaimed, alluding to a pair of premises I had lost track of—a sort of metaphysical
tristesse
came over me. Earlier, on the road, I had had a near encounter with
le néant
. Now here I was in a provincial restaurant that, to a New Yorker like myself, seemed a vestige of a departed past, the snows of yesteryear. It was as if the Copa had never left Pittsburgh. In this eerily unreal setting, I could almost feel the Spontaneity of Nothingness. Okay, it was a mood, not a philosophical argument. But it filled me with the conviction that Grünbaum’s ontological certitude—watertight, bulletproof, sunk-hinge, angle-iron, and steel-faced though it was—could not be the last word. The mystery of existence was still out there.

I was driven back to my hotel without incident. Slightly addled by the quantities of champagne and wine I had consumed, I lay down and drifted off to sleep without turning down the bedspread. The next thing I knew, the dawn light was filtering through the curtains and the phone was ringing. It was the Great Rejectionist.

“Did you sleep well?” he buoyantly asked.

5

FINITE OR INFINITE?

C
ompared to the eternal cosmos envisaged by the ancients, our own universe is something of a Johnny-come-lately. It seems to have been around a mere 14 billion years or so. And its future may well be bounded too. According to current cosmological scenarios, it is destined either to disappear abruptly in a Big Crunch some eons down the road, or to fade gradually into a dark and chill nothingness.

The temporal finitude of our universe—here today (but not yesterday), gone tomorrow—makes its existence seem all the more insecure and contingent. And mysterious. A world with solid ontological foundations, it seems, just wouldn’t behave like this. It would exist eternally and imperishably. Such a world, unlike the finite Big Bang universe, would have an aura of self-sufficiency. It might even harbor the cause of its own being.

But what if our own world, contrary to current cosmological thinking, did turn out to be eternal? Would the mystery of its existence then become less acute? Or would the sense of mystery vanish entirely?

THE TEMPORAL NATURE
of the world has long been a hotly contested issue in Western thought. Aristotle held the cosmos to be eternal, with no beginning or end in time. Islamic thinkers disagreed. The great philosopher and Sufi mystic al-Ghazālī, for instance, argued that the very idea of an infinite past was absurd. In the thirteenth century, the Catholic Church declared it to be an article of faith that the world had a beginning in time—although Saint Thomas Aquinas, showing some loyalty to the Aristotelian tradition, insisted that this could never be proved philosophically. Immanuel Kant argued that a beginning-less world led to paradox: how, he asked, could the present day ever have arrived if an infinite number of days had to pass first? Wittgenstein, too, felt there was something odd about the idea of an infinite past. Suppose, he said, you were to come across a man reciting to himself, “… 9 … 5 … 1 … 4 … 1 … 3 … finished!” Finished what? you ask him. “Oh,” he says with relief, “I’ve been reciting all the digits of π backward from eternity, and I finally got to the end.”

But is there anything truly paradoxical about an infinite past? Some thinkers object to the notion because it entails that an infinite series of tasks might have been completed before the present moment—which, they say, is impossible. But completing an infinite series of tasks is not impossible if you have an infinite amount of time in which to perform them all. In fact, it is mathematically possible to complete an infinite series of tasks in a
finite
amount of time, provided you perform them more and more quickly. Suppose you can accomplish the first task in an hour; then the second task takes you a half hour; the third takes you a quarter of an hour; the fourth takes you an eighth of an hour; and so on. At that rate, you will have finished the infinite series of tasks in a total of just two hours. In fact, every time you walk across a room you accomplish such a miracle—since, as the ancient philosopher Zeno of Elea observed, the distance you cover can be divided into an infinite number of tinier and tinier intervals.

So Kant and al-Ghazālī were wrong. There is nothing absurd about an infinite past. It is conceptually possible for there to have been an infinite succession of sunrises before the one this morning—provided there was an infinite span of time in which they could have occurred.

Scientific thinkers, by and large, have not shared such philosophical qualms about eternity. Neither Galileo nor Newton nor Einstein had any problem conceiving of a universe that was infinite in time. Indeed, Einstein added to his field equations a fudge factor—the infamous “cosmological constant”—to ensure that they would yield a universe that was static and eternal.

But astronomical observations soon revealed that, contrary to Einstein’s intuition, the universe was
not
static. It was expanding, as if from an initial explosion. Even in the face of this evidence, some cosmologists still clung to the hope that the universe might be eternal. In the late 1940s, Thomas Gold, Hermann Bondi, and Fred Hoyle proposed a theoretical model called the “Steady-State Universe,” which managed to be both expanding
and
eternal. (Gold and Bondi claimed that they came up with the idea after seeing the horror film
Dead of Night
, the dream-infused plot of which loops around on itself endlessly.) In their model, the empty space left behind by the ever-retreating galaxies is continuously filled by new particles of matter, which pop into existence spontaneously thanks to a “creation field.” Thus despite the expansion, a constant density of matter is maintained. Even though it is constantly expanding, the Steady-State Universe always looks the same. It has no beginning and no end.

Another cosmological model of eternity is the “Oscillating Universe,” which was first proposed in the 1920s by the Russian mathematician Alexander Friedmann. According to this model, our universe—the one that originated some 14 billion years ago with the Big Bang—emerged from the collapse of an earlier universe. And, like that earlier universe, ours too will eventually stop expanding and collapse back on itself. But when it does, the result will not be an all-annihilating Big Crunch. Instead, a new universe will rebound out of the fiery implosion, in what might be called the Big Bounce. And so on and so on,
ad infinitum
. In this model, time becomes an endless cycle of destruction and rebirth, rather like the dance of the god Shiva in Hindu cosmology.

Both the Steady-State Universe and the Oscillating Universe make the problem of cosmic origination go away. If the universe is infinitely old—if it has always been around, in other words—there is no “creation event” to be explained. Unfortunately for lovers of eternity, the Steady-State model is no longer taken seriously by cosmologists. It was done in by the detection, in 1965, of the background radiation left over from the Big Bang, which furnished decisive evidence that our universe had a fiery beginning after all. The Oscillating model has fared better, but it is plagued by theoretical gaps. So far, no one has been able to explain exactly what sort of unknown repulsive force could overcome the attractive pull of gravity at the last moment of collapse and cause the universe to “bounce” rather than “crunch.”

So at the moment, anyway, the odds seem to favor a finite past for our universe. But what if our universe is not all there is? What if it is a part of some greater ensemble?

One of the great lessons of the history of science is that reality always turns out to be more encompassing than anyone imagined. At the beginning of the twentieth century, our universe was thought to consist of just the Milky Way galaxy, sitting all by itself in an infinite space. Since then, we have learned that the Milky Way is merely one of a hundred billion or so similar galaxies. And that’s just the
observable
universe. The current theory that best explains the Big Bang is called the “new inflationary cosmology.” As it happens, this theory predicts that universe-engendering explosions like the Big Bang should be a fairly routine occurrence. (As one friend of mine observed, it would be very odd if the Big Bang came with a label that said, “THIS MECHANISM OPERATED ONLY ONCE.”)

In the inflationary scenario, our universe—the one that suddenly popped into existence some 14 billion years ago—bubbled out of the spacetime of a preexisting universe. Instead of being all of physical reality, it’s just an infinitesimal part of an ever-reproducing “multiverse.” Although each of the bubble universes within this multiverse had a definite beginning in time, the entire self-replicating ensemble may be infinitely old. The eternity that seemed lost with the discovery of the Big Bang is thus regained.

With an eternal world—whether of the inflationary variety or some other—there is no inexplicable “creation moment.” There is no role for a “first cause.” There are no arbitrary “initial conditions.” An eternal world thus seems to satisfy the Principle of Sufficient Reason. The way it is at any moment can be explained by the way it was the previous moment. Indeed, its
existence
at any moment can be explained by its existence the previous moment. Should that be enough to dispel any lingering sense of mystery?

Many have thought so—prominently among them, David Hume. In Hume’s
Dialogues Concerning Natural Religion
, the character Cleanthes, who comes closest to being the author’s mouthpiece, gives two arguments that an eternal world requires no explanation for its existence. “
How,” he asks, “can anything
that exists from eternity have a cause, since that relation implies a priority in time and a beginning of existence?” It is assumed here that an explanation must invoke a cause, and that a cause must come before its effect. But nothing could precede a world with an infinite past, so such a world could have no prior cause and hence no possible explanation for its existence.

There are two problems with this first argument. To begin with, nothing in the concept of causation says that a cause must always precede in time its effect. Think of a locomotive pulling a caboose: the motion of the former causes the motion of the latter, yet the two are concurrent in time. Moreover, not all explanations must invoke causes. Think, for example, of the explanation for a rule in baseball or a move in chess.

Hume’s second argument is a better one. Suppose (he has his spokesman Cleanthes say) we think of the history of the world as a series of events. If the world is eternal, this series is an infinite one, with no first or last member. Now, each event in the series can be causally explained by the event that precedes it. Since there is no event that lacks an explanation, everything seems to be explained. “Where then is the difficulty?” Cleanthes asks. He is unimpressed by the obvious rejoinder: that even if each event in the series is causally explained in terms of an earlier event, the series
as a whole
remains unexplained. For the series as a whole, he insists, is not something over and above the events of which it is composed. “I answer that the uniting of these parts into a whole, like the uniting of several distinct countries into one kingdom, or several distinct members into one body, is performed merely by an arbitrary act of the mind, and has no influence on the nature of things,” Cleanthes says. Once all the parts are explained, he submits, it’s unreasonable to demand a further explanation of the whole.

Seen in this light, an eternal world looks like the cause of itself, since everything within it is caused by something else within it. Hence it requires no external cause for its existence. It is
causa sui
—an attribute usually reserved for God.

But there’s still something missing here. This infinite world is like a railroad train with an infinite number of carriages, each pulling the one behind it—and no locomotive. It can also be likened to a vertical chain with an infinite number of links. Each of these links holds up the link below it. But what holds up the chain as a whole?

Imagine yet another sort of series that has no beginning and no end, this one consisting of an infinite succession of copies of some book—say, the
Bhagavad Gita
. Suppose that each book in the series is faithfully copied by a scribe, letter for letter, from the preceding book in the series. Now, for each given copy of the
Bhagavad Gita
, the text is fully explained by the text of the preceding copy, from which it had been transcribed. But why should the whole series of books, extending back infinitely far in time, be copies of the
Bhagavad Gita
? Why not copies of some other book—
Don Quixote
, say, or
Paradise Lost
? Why, for that matter, should there be any books at all?

The preceding thought experiment, essentially due to Leibniz, is somewhat fanciful. But it can be sharpened up and made more scientific. Suppose you want to explain why the universe is the way it is at a given moment in its history. If the universe is eternal, you can always find earlier states in its history that are causally related to the state you’re trying to explain. But knowledge of those earlier states is not enough. You must also know the
laws
that govern how one state of the universe evolves into another.

To be more precise, consider the total mass-energy of the universe as it is today. Call this mass-energy
M
. Why does
M
happen to have the value it does? To answer that question, you might point out that total mass-energy of the universe yesterday was also
M
. But that is not by itself an explanation of its value today. You also need to appeal to a law—in this case the law of mass-energy conservation. The total mass-energy of the universe today is
M
because (1) the total mass-energy of the universe yesterday was
M
and (2) mass-energy is neither created nor destroyed. Now your explanation is complete.

Or is it? It appears that there are
two
ways in which the universe could have been radically different. It could have had a different total mass-energy throughout its history—say,
M'
instead of
M
. And it could have had a different law governing that mass-energy: a law that, for example, might have allowed the mass-energy to cycle back and forth over time between a pair of values,
M
and
M
ˇ
. (To return to the
Bhagavad Gita
example for a moment, that would be as if the text kept getting translated back and forth from Sanskrit to English to Sanskrit to English and so on.) We still have no explanation of why there is
this
law and
this
precise value. Both appear to be contingent. Nor do we (yet) have an explanation of why there should be any mass-energy at all, let alone a law governing it. An eternal world can still be a mysterious world.

But we knew this intuitively already. Even if something is
causa sui
, its existence can still seem arbitrary. And an entity needn’t be eternal to be self-caused. It could also trace out a circular path in time, looping around on itself so that it has no beginning and no end. Something of the sort can be found in the 1980 movie
Somewhere in Time
. The main character (played by Christopher Reeve) is given a gold watch by an old woman. He then travels back in time and gives the watch to the same woman when she was in her youth—the very watch that she will, some decades later, give to him. How did this watch come into being? In its entire existence, which spans only a few decades, it never sees the inside of a watch factory. It exists even though it has no creator. It seems to be
causa sui
. (Some physicists call an entity with such a circular history a
jinn,
since, like Aladdin’s genie, it seems to be self-conjuring.) The existence of this gold watch is as inexplicable as the existence of the poem “Kubla Khan” would be if I had gone back in time to the autumn of 1797 and dictated it to a grateful Coleridge, who then published it so that two centuries later I could learn it by heart.