Tuesday, March 19, 2013

Lawrence Krauss, David Alpert, Jim Holt, Freeman Dyson



Philosophy, Physics and the Great Kerfuffle

            Recently there has been quite a kerfuffle about a review by David Alpert of Lawrence Krauss’s book A Universe from Nothing in the New York Times.  Stung, Krauss has been on something of a war path directed against “philosophers” generally.  Meanwhile I was quite smitten this year with Why Does the World Exist?, an excellent little book by the science writer Jim Holt.  Much to my dismay this book was slammed, along with philosophers in general, in a (to my mind) very self-indulgent review in the New York Review of Books by the distinguished physicist Freeman Dyson.  That finally spurred me to get in my own two cents.

I.  Origins of the Great Kerfuffle

The initial motivation for the title, A Universe From Nothing, and indeed the whole project was essentially polemical: if the physicist can show how something came from nothing there is no need to postulate God as the creator.  A powerful blow struck for atheism!  That was the idea.  That was the (polemical, not scientific) original mistake, an unfortunate but tempting choice of words that led Professor Krauss to try, quixotically, to redefine “nothing,” that caused the kerfuffle.  Professor Krauss’s own reputation is based on his excellent popularizations including The Physics of Star Trek (which I read with great pleasure) and Quantum Man, his biography of Richard Feynman, among several other volumes, and on his enthusiastic participation in the contemporary “New Atheist” movement.  He was a close associate of the late essayist Christopher Hitchens and continues to work with the polemical biologist Richard Dawkins (both of whom, I want to stress, I admire greatly.  I have spent many hours reading both Hitchens and Dawkins.  I was gratified once to be quoted, although not by Dawkins himself, on Dawkins’ own very large and lively blog).  Dawkins provided Krauss’s book with an embarrassingly over-the-top jacket blurb: “Even the last remaining trump card of the theologian, ‘Why is there something rather than nothing?’ shrivels up before your eyes as you read these pages. If On the Origin of Species was biology’s deadliest blow to super­naturalism, we may come to see A Universe From Nothing as the equivalent from cosmology. The title means exactly what it says. And what it says is ­devastating.”

Except that, as Alpert pointed out, it’s not devastating for any actual cosmogony, religious or otherwise, not only because physicists cannot, as I will follow Alpert in arguing, show that the universe came from nothing, but because “theologians” (Dawkins’ term for believers) are equally unable to do so: they claim that the universe came from God.  If someone claimed that God “came from nothing” (I would be genuinely curious to hear of anyone who ever claimed that) they would have the exact same problem as the physicists do, whether or not they abjured the need for some kind of causal explanation (an option that physicists, by definition, do not have).  Neither physical nor “theological” explanations can use the concept of nothingness in any kind of explanation whatever.  What is vexatious to the atheist vanguard is that no physicist or biologist is ever going to prove that there is no God, because that is not an empirical question: they are heavily invested in a particular philosophy of knowledge, and when one claims not to have any philosophy at all one is in particular danger of being led astray by one’s philosophy (since everyone has some philosophy or other, regardless of whether they care to or wish to). 

It is quite misdirected, though, to direct this anger at philosophers, a mixed bag of people including, probably, a majority of atheists (like me) with a generous sprinkling of believers and one of the few contemporary groups of professional academics who continue to welcome study and debate on issues of faith.  In fact there is a philosophical discussion that is (unlike big bang cosmogony or evolutionary biology) genuinely subversive of religious and specifically creationist belief, and that is the logical question about the apparent contingency of existence.  There are large numbers of people who are committed to the necessary existence of God.  Admittedly, a believer could acknowledge that there might have been no God (that the existence of God is contingent), but insist that there is one, but most believers, and certainly most creationists, take the position that God necessarily exists.  If this is true then an argument that subverts the notion that there is a reason to think that something exists necessarily is going to be, unlike the empirical arguments of the scientists, genuinely subversive for believers.  In fact the only arguments that could even possibly support atheism with actual reasons are logical arguments and not empirical ones.

No one reading this has any reason to think that something ever “came from” nothing, whatever that means.  One could mean at least two things by saying that something came from nothing: first, one could simply mean that there was once nothing and then something appeared.  This interpretation does not implicate “nothing” in the appearance of something.  On this interpretation it’s not precise to say that something came “from” nothing; the absence of anything merely preceded the appearance of something (I am setting aside here a technical problem raised by big bang cosmology, whereby space and time as we experience them are not present in the “singularity”).  This interpretation requires that the appearance of something was uncaused, since there was nothing to play any causal role in the appearance of something.  Maybe every event doesn’t have to have a cause (can anybody show that they must?), and maybe we could go even further and say that the appearance of something is an event that couldn’t have a cause, since nothing preceded that event that could have played a causal role; different people will feel more or less comfortable leaving it at that.  A perhaps more attractive alternative, though, is to doubt (as I do) that at any point something came from nothing, especially since no one reading this has any reason to think that it did.  But on either alternative – that the appearance of something was an uncaused event, or that such an event never occurred – there is no work for physics to do.

The sterility of that conclusion, though, may be another reason why some physicists prefer to investigate the second possible interpretation, which is that something actually came from nothing, that is, that there was something about nothing that played a causal role in the origin of the universe.  This interpretation raises the further question as to whether, given whatever it was about nothing that caused our universe to appear, this causal process was nomological (law-like), versus contingent.  This is important because an explanation from physics would have to appeal to some nomological principles or other to be an explanation from physics, and there’s no a priori reason to think that existence (the presence of something) is necessary, much less to think that, necessarily, something came from nothing, which means that there is no a priori reason to think that physics can (even theoretically, even with hand-waving towards some “knowledge” that we currently lack) explain the appearance of something starting from the assumption that there was an initial “state” (actually it’s not a state) of nothing.

One reason for the interest among physicists in “something from nothing” is the big bang theory itself.  On this theory there was a “singularity” (very roughly this is a state of matter/energy so dense that it is immeasurable) about 14 billion years ago and then a rapid expansion and cooling into the present universe.  This sounds a lot like something from nothing, but it isn’t.  It’s the present something from an anterior something (the singularity).  Moreover some physicists (including Lawrence Krauss) are interested in “multiverse” theories, theories that hold that there could be multiple universes.  On multiverse theories big bang-type events could be happening many times.  The story of the big bang, in short, is not the story of the origin of existence.  It is the story of the origin of this particular universe from another state of being that preceded it.  When Hawking says that if you give him, roughly, the force of gravity he can get you the rest of the universe, or Krauss says that if you give him, roughly, quantum dynamism he can get you the rest of the universe, that’s impressive but not the same as explaining how something came from nothing, nor does anyone need to follow the technical reasoning (or even to read the books) to know that.  In fact none of the recent popular physics books on cosmogony actually even tries to explain how there was nothing and then there was something.  They all begin with something or other and then try to show (whether successfully or not is irrelevant) how more something can be got from the initial something.  That includes “laws”: it may or may not be incoherent to say that there could be a “law” (whatever that is) in the absence of anything else, but the obtaining of a “law,” whatever that is, is not the same thing as nothing.  Physics can only explain how some state of affairs (such as the presence of the force of gravity) led to, or relates to, some other state of affairs (such as the presence of the rest of the universe), and nothing does not qualify as a “state of affairs,” although that merits some discussion and I’ll get back to that.

I don’t mean to imply that all, or even most, physicists don’t understand this (and of many of those about whom one might say “they don’t understand” it would be more accurate to say that “they’re not interested,” which is, I want to stress, just fine).  Steven Weinberg has said, “Why there is something rather than nothing (is) just the kind of question that we will be stuck with when we have a final theory (of physics). … We will be left facing the irreducible mystery because whatever our theory is, no matter how mathematically consistent and logically consistent the theory is, there will always be the alternative that, well, perhaps there could have been nothing at all.”  Right, that is the philosophical issue: the apparent contingency of existence.  Is there any “problem” here?  There is at least one coherent question: do we know that existence is contingent?  This is not a question for physics or, at least, no one reading this can explain how the method of physics even in principle addresses this question (as Weinberg, for one, understands).  

If this juncture is a parting of the ways, though, one of the two parties is going to have to take “cosmogony” with them.  My sense is that cosmogony should go with the physicists.  The sense of the word has changed over the centuries as the sense of the word “universe” has changed.  In ancient times (and etymologically) “universe” means the totality of everything that exists, what I’ve been calling “existence” itself, and thus the proper subject of the philosophical discussion about the contingency of said totality.  But nowadays “universe” has a more specific meaning reflecting the progress of physics in constructing a model of this universe, the one we live in.  This is ultimately a question of usage, but “cosmogony” on most contemporary tongues refers to big bang theory and other discussions in astrophysics that pertain to the age and origins of this (specific) universe (which, the physicists and logicians agree, is not necessarily the only universe there is).  Besides, the philosophical question at hand is not ultimately about the origin of existence (if, as I doubt, existence ever had an origin), rather it is about whether existence is contingent or necessary.

II. Is the contingency of existence logically demonstrable? 

The philosophical discussion of the contingency of existence uses “existence” in a more traditional, generic sense to refer to anything that exists, what we can just call “existence,” as opposed to the physicists’ tendency to conflate “existence” with “the universe” (or “the multiverse”).  As mentioned earlier that discussion need not take it as axiomatic that existence ever had a beginning at all, or that if existence did have a beginning that event was caused, or that there was ever any event such that before the event nothing existed and after the event something existed, because no one reading this has any conceivable reasons for claiming to know that any of those things are true.  No matter how existence, which is not logically identical to our universe, got started (on the dubious assumption that it ever did), or even, as it seems more sensible to think, it never got started at all, one can still ask the question about its contingency.  So physics rightly takes “cosmogony” (and I’m sure it’s in good hands) and the philosophers are left with the question about the contingency of existence, which is a (very deep and strange) question for modal logic.  

Modal logic deals with possibility and probability: we say about different ways things could be (“states of affairs” is the term of art) that they are possible or impossible, contingent or necessary, probable or improbable.  The way that these terms are formally modeled by logicians is with “possible worlds”: a possible world is a world where some state of affairs could “obtain” (please bear with the jargon, it’s really quite manageable and it does make things easier).  These “worlds” can be thought of as universes: maximal states of affairs.  To say that something is possible is to say that there is a possible world where that state of affairs obtains, while an impossible state of affairs is one that does not obtain in any possible world.  A contingent state of affairs does not obtain in at least one possible world; a necessary state of affairs obtains in all possible worlds.  Probability, of course, has to do with the obtaining of a state of affairs in relative numbers of possible worlds.  This is a colorful way of talking that lends the subject a fanciful air, but in fact modeling modal operators as quantifications over sets of possible worlds is a very concrete way of representing things, which makes it possible for binary computers (those very literal-minded creatures) to represent these relations, which makes contemporary computation possible.  Hippy stuff, to be sure, but very important hippy stuff.

In the “possible worlds” paradigm of modal logic there is no world where there is nothing.  This is because the only coherent definition of a world is the definition of what exists “in” that world.  As the philosopher David Lewis wrote in his fascinating book On the Plurality of Worlds, a world is not like the bottle that holds the beer.  What would count to distinguish one empty world from another?  (Possible worlds, which are only logical constructs, do not share with each other the space and time of some larger encompassing universe.)  In fact if a world just is what exists in that world, then a “world” where nothing exists is incoherent.  The only coherent idea of the universe is the idea of all of the things that are present in it: those things just are the universe.  If nothing existed there would be no world (universe), which is not at all the same thing as an empty world.  This is the corollary to the earlier point that physics can’t explain (and has no need to explain) how something came from nothing.

Ordinarily we want to somehow represent to ourselves what we are thinking about (Kant famously argued that all of our thinking is limited and structured by our ability to represent).  In fact this representative function is often just identical with thinking (it is interesting to consider the example of physics itself here; reading the autobiographical popularizations of both the relativity theorist Einstein and the quantum theorist Feynman one gets the sense that some kind of visualization is nearly synonymous with thought for both men).  In the case of the contingency of existence what we are tempted to do is to picture, say, a spiral galaxy against the background of black space, and then – poof! -  imagine the galaxy disappearing, leaving only “void,” in this case a black space in the mind’s eye.  But this is a misleading way to represent nothingness.  Any way of representing nothingness is misleading.  If nothing existed there would be no universe, no space, and no void.  There wouldn’t be anything that was empty or devoid of matter/energy.  It may or may not be incoherent to say that existence is contingent (that’s part of the philosophical question), but it is surely incoherent to say that one could imagine what nothingness would be like, because it wouldn’t be like anything.  It wouldn’t be a state of affairs in a world.  Thus it cannot be represented.

Now we can see how thinking about the apparent contingency of existence gets us into a mind-bending situation, and how the problem is essentially philosophical: many people, including Steven Weinberg and myself, share the intuition that existence is contingent.  But our formal logical definition of contingency is “false in some possible world.”  But the absence of anything cannot be thought of as a state of affairs in a possible world.  So we must, disconcertingly, step outside of our ordinary conception of modality and our ordinary sense of “contingent.”  The proposition under consideration is: That there exists at least one world is a contingent fact.  It is not necessary that there be any worlds, including this one.  Put this way the proposition appears to be question-begging: how could we know that existence is contingent?  Would justifying the belief that existence is contingent require a demonstration of the necessity of the contingency of existence? 

Rationalists like Rene Descartes thought that a demonstration of the logical necessity of the truth of a proposition (as in mathematics) was the only acceptable (indubitable) standard of justification of a belief.  Notoriously Descartes then ran himself around in circles, arguing, for example, that we could prove God’s existence by appealing to the evidence of our reason and that we could trust in our reason by appeal to the goodness of God.  He lacked the magical initial premises that would bring the necessity of existence along in their train, because there aren’t any.  Even the premise that God exists is merely regressive: where did God come from?  Empiricists like David Hume, on the other hand, saw “justification” as a matter of demonstrable probability, as in empirical science, not logical certainty.  Of course empiricists (including physicists) don’t actually bother (previously-discussed misunderstandings notwithstanding) with trying to prove that existence is necessary or that it is contingent.  That’s just not an empirical question.  That’s because the problem empiricism would have with demonstrating that there must (or needn’t) be something that exists is that there is only one “fact” in the data set (namely, something exists): no probabilities there.  A singular fact can underwrite no empirical law: “laws,” on the empiricist’s view, are expectations (inductions) about the future grounded in regularities of past and present experience.  Conversely one cannot generate some set of natural laws (generalizations) that explain (deduce) the necessity or contingency of existence. 

We philosophers find ourselves, for the thousandth time, foundering in deep water, having been, for the thousandth time, abandoned a while back by our more sensible scientific brethren.  Or more likely it was we who wandered off, hopefully without forgetting to bring the lotus leaves.  Some things never change!  But there is more than one way to go from here.  One attractive option is to argue that the contingency of existence is not a proper object of knowledge: we neither “know” nor do we “not know” that existence is contingent.  The argument is that there are necessary conditions for the proper use of the verb “to know,” and the contingency of existence doesn’t meet those conditions.  When I tell you that I know where my car keys are that is informative, it means something, because I might not have known that: you didn’t know whether or not I knew until I told you, and now you do, and your knowing may have practical significance for both of us.  Also I could be mistaken: you could show that even though I believe that I know where the keys are, in fact I do not know that.  When those conditions (when it’s informative to find out that I know or don’t know and when it’s possible that I could be mistaken) do not obtain there cannot be any coherent (meaningful) use of that verb.  Basically this is an instrumentalist theory of meaning.  I think that this argument is persuasive when, for example, someone tries to tell me that I don’t “know” if the external world exists.  The right response is to say that I neither know nor do I not know (the world of experience is the “ground” of knowing and not a proper object of knowledge itself):  the skeptic is posing a pseudo-problem.

Is the question about the contingency of existence like the question about the existence of the external world?  In neither case would the respective alternatives be reflected in experience.  If the skeptic is right to suggest that the external world might not exist, that means that it might not exist right now and our experiences have some other sort of explanation.  Of course that’s exactly what’s incoherent about the skeptical  suggestion: as Hume saw clearly, it’s not “explanatory” to say that the external world does exist.  That claim is just as incoherent as claiming it might not, because both claims go beyond experience, which, for Hume, was the only possible basis for knowing anything.  Now consider the claim that existence might be either contingent or necessary.  In possible-worlds modeling the necessity or contingence of some state of affairs at some possible world makes sense in the context of other possible worlds (other ways that the world could be).  But in the case of the alleged contingency of existence the only choices are existence and nothing.  Existence cannot be the cause of itself.  Since there is no other variable at all there can be no other relevant variable: nothing else could possibly show that existence was either necessary or contingent.  This parallels the situation where the skeptic is making claims about my knowledge of the existence of the external world: just as “I know that the external world exists” and “I don’t know that the external world exists” are equally meaningless propositions, so “I know that existence is contingent” and “I know that existence is necessary” are equally meaningless.  So one plausible response to the question is to say that there isn’t really a logical problem here at all, just as the global skeptic’s epistemological question is really a pseudo problem.  This kind of argument from criteria for meaningfulness can appear to be a mere throwing up of the hands but that is an underestimation: it is real progress to show that the skeptical problem of the external world is a pseudo problem, and in fact much of the world has not caught up with this argument (that was developed by Wittgenstein but that is already present in Hume).

However, although the Hume/Wittgenstein argument to the effect that global skepticism is a pseudo-problem is one that I find both persuasive and satisfying, I cannot shake the intuition that existence is contingent.  That is, I cannot shake the intuition that it is somehow a meaningful statement to say “Existence is contingent.”

III.  Here is my (unpublished) letter to the New York Review of Books provoked by Freeman Dyson's review in that publication of Jim Holt's Why Does the World Exist?



Editors                                                                                                                                                                                  New York Review of Books

To the Editors:

                Having immensely enjoyed Jim Holt’s excellent Why Does the World Exist?, and being an avid reader of  all of the writing on physics in NYRB, including Freeman Dyson’s, I was eager to read Professor Dyson’s review of Holt’s book in your most recent issue.  Indeed I brought it home from the post office and sat down and read it on the spot.  I am compelled to write partially in defense of Mr. Holt, and partially because there are some interesting issues here, but also out of unexpected disappointment.

                At the beginning of the twenty-first-century there is no doubt that physics is the preeminent science of the past one hundred years and of the foreseeable future, certainly for the popular culture, and notwithstanding the epochal advances of biology and chemistry, and the physical sciences in general, during the same time.  Educated lay people around the world can name many twentieth-century physicists, from Einstein, Bohr and Schrodinger to Feynman, Hawkins and Weinberg.  Their cultural status is of the highest, their real achievements are stunning, and their popular writings and biographies are avidly read by millions.  The same cannot be said for philosophy.  Most lay people could not name more than two or three of the leading philosophers of the past century, and their ideas are even more obscure than their names.  Only a tiny elite of professional philosophers command high salaries, while the rest labor in tenuous circumstances, publishing an insular literature that is unknown to the public.  While a physicist today is synonymous with a powerful intellectual, philosophers are as often as not regarded as vaguely subversive charlatans, condemned from the right as lotus-eaters and from the left as obtuse logicians, acknowledged all around as writers of impenetrable jargon.

                Then why, oh why do physicists have such a raw resentment of philosophers?  It goes beyond the usual xenophobic inter-departmental food fight familiar to every university professor in the land.  On that tedious tribal level it makes no more sense for the old silverback physicists to snarl at philosophers than at, say, geologists, or poets.  Part of it can no doubt be explained by the fact that the awkward duty has recently fallen to the low-status philosophers to explain to the high-status physicists that no natural scientist can, even in principle, explain how something could have come from nothing, since natural science by definition must appeal to some accepted constants to make a case for some causal relationship between existing entities and circumstances.  That’s how natural scientists, including physicists, develop testable hypotheses that can be proven or disproven by experiment – something they are fond of throwing up to philosophers.  Nothingness cannot enter in to such relations.  The point is indisputable, but of course that very fact only enrages the high-status physicists even more (we’re all most angry when we’re wrong).  Then there is the matter of the concept of “nothing.”  Physicists, whose purview is the actual, existing universe, have no reason to think about the essentially logical concept of nothing (they sometimes say that it is the philosophers who do not understand “nothing,” and then go on to explain that nothing is something - “gravity,” say, or ”quantum perturbations” - after all).  There is also no reason to think that thinking about the concept of nothing could ever have any practical application.  Nor is there any reason, as to that, to think that something ever came from nothing in the first place.  The physicist’s rebuke of the lowly philosopher for this impertinence is unattractive, but philosophers (many of whom are adoring physics groupies, by the way) tend not to mind unattractiveness.  It is worse to be uninteresting, and I’ll venture a further impertinence: m’lord’s wrath on this point is not of philosophical interest.

                Philosophers have not much better luck, but from the logical point of view the question is at least interesting.  The question is, “Is existence contingent?”  Contemporary modal logic formalizes modal operators (“necessary,” “contingent,” “possible,” “impossible,” “probable,” “improbable”) by quantifying over sets of possible worlds.  This sounds fantastic but it is, among other things, the only way to enable computers, those most literal of creatures, to handle modality.  So in the case of contingency, the proposition “X is contingent” is analyzed: “X is false in at least one possible world,” possible worlds being understood as ways the world could be.  But the proposition “Existence is contingent” cannot be analyzed in this conventional way.  To say “There is at least one possible world where nothing exists” is to posit a possible world, and a possible world is still something, just as the null set is still a set.  So it seems that there is no way to logically model of the contingency of existence.  Of course one cannot construct a "possible worlds" model of the necessity of existence either, for the same reason.  Just as traditional skepticism is best appreciated as pressuring our standards for justifying beliefs, rather than our ordinary beliefs themselves, so the question about the contingency of existence puts some interesting pressure on our understanding of modal logic.  (Of course different people will have different intuitions about the contingency of existence.  I for one can’t shake it.)

                Professor Dyson has nothing to say about any of this.  In fact he finds nothing to discuss anywhere in Mr. Holt’s delightful book.  He simply uses the occasion as an opportunity to slam philosophers and philosophy.  He claims that he appreciates philosophy as literature and laments, more in sadness than in anger, that philosophy is not what it used to be.  It’s true that philosophers used to be polymaths.  The great seventeenth-century rationalists were mathematicians and physicists, and fourth-century BCE Greeks would have had to be instructed for some time to understand how a philosopher and a physicist and a psychologist were not all doing the same thing (if you could ever get them to accept that).  But we live in a different time.  Few lay people today could name the greatest contemporary biologists or chemists, or the greatest poets or literary critics.  The role of the individual thinker has changed in profound ways since the days of Aristotle or of Leibniz.  Professor Dyson’s lament is equivalent to saying that young people don’t have values like people used to do, a complaint prominent in Plato’s writings.

Jim Holt interviewed physicists and philosophers, a fact Professor Dyson acknowledges about halfway through this non-review.  Professor Dyson dispenses with this complication by defining all of the physicists who spoke to Holt (one chapter is devoted to Steven Weinberg) as physicists who use physics as “a basis for philosophical speculation,” and then simply goes on to lump them in as philosophers with the rest.  One wouldn’t know from this review that the book includes more pages dedicated to discussion with physicists and cosmologists than it does with philosophers. Professor Dyson’s last line is supposed to be the kicker, the one to make us all stare into our beer: “Modern departments of philosophy have no place for the mystical.”    But quite a few of both the Dyson-designated “philosophers” (Roger Penrose, David Deutsch, John Leslie) and the actual philosophers (Richard Swinburne, Derek Parfit) interviewed here are unabashed mystics.  Professor Dyson’s assertion is merely bizarre, and his qualifications for making it are none.  The only interesting question he raises is the one I started with: what are philosophers doing that gets up the noses of physicists so much?  They must be doing something right.