Philosophers confused over causality

Physicists usually have a dim view of philosophers. One reason is that philosophers reject causality.

Here is a new philosophy paper with more nonsense on the issue:

Issues surrounding the role of causation/causal reasoning in physics have recently been the subject of considerable philosophical discussion (e.g., Norton, 2009, Smith, 2013, Frisch, 2014). There is a spectrum (or perhaps, more accurately, a multi-dimensional space) of different possible positions on this issue: Some, echoing Russell, 1912 take the view that features of fundamental physical laws or the contexts in which these laws are applied imply that causal notions play little or no legitimate role in physics – or at least that they play no “fundamental” role. Others take the even stronger position that causal notions are fundamentally unclear in general and that they are simply a source of confusion when we attempt to apply them to physics contexts (and presumably elsewhere as well. ) A more moderate position is that while causal notions are sometimes legitimate in physics, they are unnecessary in the sense that whatever scientifically respectable content they have can be expressed without reference to causality. Still others (e. g., Frisch, 2014) defend the legitimacy and even centrality of causal notions in the interpretation of physical theories. Those advocating this last position observe that even a casual look at the physics literature turns up plenty of references to “causality” and “causality conditions”. Examples include a micro-causality condition in quantum field theory which says that operators at spacelike separation commute and which is commonly motivated by the claim that events at such separation do not interact causally, and the clustering decomposition assumption referred to in section 5 which is also often motivated as a causality condition. Another example is the preference for “retarded” over “advanced” solutions to the equations of classical electromagnetism (as well as the use of retarded rather than advanced Green’s functions in modeling dispersion relations, as discussed below) where this is motivated by the claim that the advanced solutions represent “non-causal” behavior in which effects temporally precede their causes (violation of another causality condition). Similarly, there is a hierarchy of causality conditions often imposed in models of General Relativity, with, for example, solutions involving closed timelike curves being rejected by some on the grounds they violate “causality”. Causal skeptics (e.g., Norton, 2009 and to some extent, Smith, 2013) respond, however, that these conditions are either unmotivated (because, e.g., vague or unreasonably aprioristic) or superfluous in the sense that what is defensible in them can be restated without reference to any notion of causation.

This is hopelessly confused. If a philosopher cannot see that causality is essential to modern physics, then he has no understanding of physics.

Denying that physics is about causality is like denying that physics is about energy.

Even the guy (Frisch), who defends causal notions in physics, is also confused. See his paper (pdf), where he only allows for causality in the narrowest subfields of physics. His arguments have no merit either.

There are several arguments in play, all nutty. One is that a theory making precise predictions is not causal, because the outcomes are constrained by the math, not the cause. So Newton's F = ma is not causal. Another is that action at a distance is not causal, because it cannot be broken into a chain of events. So Newtonian gravity is not causal. Another is that time-symmetric theories cannot be causal, because the past has to cause the future without the future causing the past. Most physics differential equations are time symmetric, so this eliminates a lot of theories. Another is that indeterministic theories cannot be causal, because outcomes should be determined by the causes, and not by chance. So quantum mechanics cannot be causal.

Of course stochastic theories can be causal. Without getting into mathematical definitions, consider the statement "smoking causes lung cancer". Everyone understands this. But smoking does not cause lung cancer in every single smoker, and is not the sole cause of lung cancer. Smoking raises the probability of lung cancer. It has always been understood that causality can work with probability in this way.

Statements like "the moon causes the tides" are also widely accepted under either Newtonian gravity or general relativity. Under Newtonian gravity, you might object that there was no local causality, but there was non-local causality.

Philosophers do not just attack physics. Some have attacked evolution biology, in the Causalist-Statisticalist Debate. Here is a recent review of this issue. The argument is that principles like "survival of the fittest" have no predictive power, and do not give causal explanation. They just give a framework for generating statistics about nature.

More on Musser's spooky book

SciAm editor George Musser complains that I trashed his book without reading it. Okay, fair point. His book is on Amazon as Spooky Action at a Distance: The Phenomenon That Reimagines Space and Time -- and What It Means for Black Holes, the Big Bang, and Theories of Everything.

The endorsement from Frank Wilczek says:

Locality has been a fruitful and reliable principle, guiding us to the triumphs of twentieth-century physics. Yet the consequences of local laws in quantum theory can seem 'spooky' and nonlocal-and some theorists are questioning locality itself. Spooky Action at a Distance is a lively introduction to these fascinating paradoxes and speculations.

Wilczek is a distinguished and level-headed physicist. I read this as saying that he firmly believes in locality as a great triumph of XX century physics. Some quantum experiments may seem spooky and nonlocal, so they are fun to talk about, but he is not endorsing any spooky or nonlocal interpretations or speculations that are in the book.

I can agree with that. Maybe Musser put "spooky" in the title to sell more books. If so, I do not fault him for that, as long as he describes the physics correctly.

I was once appalled by a 1979 book called The Dancing Wu Li Masters: An Overview of the New Physics. While the book was filled with goofy speculations, the actual description of the known physics was pretty accurate. So I ultimately decided that it was a decent book.

The current SciAm has a preview of his book, where he relates nonlocality to general relativity:

When I first learned about the quantum phenomenon known as nonlocality in the early 1990s, I was a graduate student. But I didn't hear about it from my quantum-mechanics professor: he didn't see fit to so much as mention it. Browsing in a local bookshop, I picked up a newly published work, The Conscious Universe, which startled me with its claim that “no previous discovery has posed more challenges to our sense of everyday reality” than nonlocality. The phenomenon had the taste of forbidden fruit. ...

Points in the gravitational field must be interlinked with one another so that they can flop around while collectively still producing the same internal arrangement of objects. These linkages violate the principle that individual locations in space have an autonomous existence. Marolf has put it this way: “Any theory of gravity is not a local field theory. Even classically there are important constraint equations. The field at this point in spacetime and the field at this point in spacetime are not independent.” ...

In short, Einstein's theory is nonlocal in a more subtle and insidious way than Newton's theory of gravity was. Newtonian gravity acted at a distance, but at least it operated within a framework of absolute space. Einsteinian gravity has no such element of wizardry; its effects ripple through the universe at the speed of light. Yet it demolishes the framework, violating locality in what was, for Einstein, its most basic sense: the stipulation that all things have a location. General relativity confounds our intuitive picture of space as a kind of container in which material objects reside and forces us to search for an entirely new conception of place.

I have no quarrel with this, except that I would not use the word "locality" this way. To me, locality means that the physics of a point can be understood from tevents, matter, and fields in its local neighborhood. General relativity satisfies locality in that sense. Musser says that relativity makes a global definition of location more difficult. Yes, that's right, but I would say that is a consequence of locality, not a contradiction to locality.

Update: Motl has just posted a good explanation of locality, and why it is a mistake to give up locality in order to get a more intuitive understanding of quantum mechanics. The spookiness of nonlocality is always less intuitive. I will respond to the first comment below tomorrow.

SciAm book promotes spooky action

Physicist Sabine Hossenfelder blogs this book review:

Spooky Action at a Distance: The Phenomenon That Reimagines Space and Time -- and What It Means for Black Holes, the Big Bang, and Theories of Everything
By George Musser
Scientific American, To be released November 3, 2015

“Spooky Action at a Distance” explores the question Why aren’t you here? And if you aren’t here, what is it that prevents you from being here? Trying to answer this simple-sounding question leads you down a rabbit hole where you have to discuss the nature of space and time with many-world proponents and philosophers. In his book, George reports back what he’s found down in the rabbit hole.

Locality and non-locality are topics as confusing as controversial, both in- and outside the community, and George’s book is a great introduction to an intriguing development in contemporary physics. It’s a courageous book. I can only imagine how much headache writing it must have been, after I once organized a workshop on nonlocality and realized that no two people could agree on what they even meant with the word. ...

In his book, George lays out how the attitude of scientists towards nonlocality has gone from acceptance to rejection and makes a case that now the pendulum is swinging back to acceptance again. I think he is right that this is the current trend (thus the workshop).

This sums up what is wrong with physics today. Clear-eyed XX century physicists purged the medieval spooky mysticism of nonlocality from science, and now it is back with no one even knowing what it is.

She goes on to say that the book is a confusing mish-mash of buzzwords and personalities, without ever explaining the physics or saying what is accepted:

I found the book somewhat challenging to read because I was constantly trying to translate George’s metaphors back into equations and I didn’t always succeed. But then that’s a general problem I have with popular science books and I can’t blame George for this. I have another complaint though, which his that George covers a lot of different research in rapid succession without adding qualifiers about these research programs’ shortcomings. There’s quantum graphity and string theory and black holes in AdS and causal sets and then there’s many worlds. The reader might be left with the mistaken impression that these topics are somehow all related with each other. ...

For my taste it’s a little too heavy on person-stories, but then that seems to be the style of science writing today.

This sums up what is wrong with popular science writing. SciAm used to be better than this.

A friend of hers wrote the book, and she recommends it. Sigh.

The Wikipedia article on action at a distance is pretty good. It explains how Maxwell developed his electromagnetic theory by seeking to get rid of action at a distance. This was one of the most important intellectual developments of all time.

To date, all experiments testing Bell-type inequalities in situations analogous to the EPR thought experiment have results consistent with the predictions of quantum mechanics, suggesting that local hidden variables theories can be ruled out. Whether or not this is interpreted as evidence for nonlocality depends on one's interpretation of quantum mechanics.

That's right. You can interpret quantum mechanics to give a scientific causal view of the world, or you can interpret it to allow for unverifiable spooky actions. Your choice. Apparently the current trend among physicists and popular science writers is for the latter.

Lawrence M. Krauss has a pretty good entanglement article in the latest New Yorker mag:

No area of physics causes more confusion, not just among the general public but also among physicists, than quantum mechanics. On the one hand, it’s the source of New Age mythology, and has enabled hucksters to peddle new self-help cures; on the other, for the philosophically inclined, it has provided some illusory hope of free will in an otherwise deterministic universe. Of the aspects of quantum mechanics that confuse and dismay observers, perhaps nothing approaches the property called “entanglement.” Einstein, who never really accepted entanglement’s existence, called it, derisively, “spooky action at a distance.”

Unfortunately for Einstein, entanglement, “spooky” or not, is apparently real, as researchers in the Netherlands demonstrated last week, just in time for Halloween. In doing so, the researchers affirmed once again that quantum mechanics, as strange as it may seem, works in every way we can test it.

Yes, physicists themselves cannot agree on whether entanglement is spooky.

He attacks the essay I cited last week:

Similarly, last week, the Pulitzer prize-winning writer Marilynne Robinson published an essay in which she challenges the nature and relevance of modern science. The essay argued that entanglement “raises fundamental questions about time and space, and therefore about causality.” She went on to say that this called into question the ability of science to explain reality as a whole. It’s easy to understand how Robinson arrived at this incorrect idea: when a measurement of one electron here can instantaneously affect the measurement of another electron on the opposite side of the universe, faster than the speed of light, it does seem as though causality has been thrown out the window.

Yes, fundamental questions about causality would be raised if the "measurement of one electron here can instantaneously affect the measurement of another electron on the opposite side of the universe". But it cannot.

Krauss's explanation is above average, but defective:

As long as the two electrons remain entangled, then this link endures — even if they are separated across the galaxy. If I measure one electron in my lab, the second electron is affected by the measurement of the first electron with no time delay — instantaneously — even though a signal travelling at the speed of light would take millenia to cross the distance between them.

That instantaneous link is the “spooky action at a distance” of which Einstein was so skeptical.

No, measuring an electron does not affect a distant electron.

Quantum mechanics gives a mathematical representation of the electron pair, and a way of making probabilistic predictions about spin. Measuring one electron does affect the prediction being made for the other. But the math is not the same as the physics. The actual electrons may be deterministic and separable.

Spooky action at a distance was debated by physicists in the time of Newton, of Maxwell, and of Bohr and Einstein. I thought that mainstream physics was solidly convinced that no such thing exists. Maybe that was true 50 years ago. What happened? Why have all these otherwise-hard-headed guys gone mushy about physics that perfected in 1930? Physics is in a sorry state when you have to read the Lubos Motl blog or my own to find something sensible on this subject.

Speculation about NSA and quantum computing

I posted a couple of months ago that NSA is cautious about quantum computers. The NSA is a secretive govt spy agency that does very little to explain itself, so there is a lot of speculation about why it would become cautious about quantum computing. Does it know something we don't?

One could also ask why Microsoft and Google are excited about quantum computing. Do they know something that we don't?

As I have often noted on this blog, quantum computing has been a colossal failure, and has no hope of any commercial applications in the foreseeable future. It is doubtful whether it is even physically possible.

Cryptography professor Matthew Green writes:

If you’re looking for a nice dose of crypto conspiracy theorizing and want to read a paper by some very knowledgeable cryptographers, I have just the paper for you. Titled “A Riddle Wrapped in an Enigma” by Neal Koblitz and Alfred J. Menezes, it tackles one of the great mysteries of the year 2015. Namely: why did the NSA just freak out and throw its Suite B program down the toilet?

These guys are leading experts in elliptic curve cryptography, and long-time NSA watchers. So their speculation is probably better than mine.

The popular press has somehow convinced everyone that Snowden proved the NSA has tricked people into using elliptic curves in order to use a pseudorandom number generator that has an NSA trapdoor, thereby allowing the NSA to spy on everyone.

This story is exaggerated. The so-called trapdoor was publicly known without Snowden, and no one had to use it. The basic elliptic curve technology remains sound.

It is curious that the NSA has deprecated the P-256 elliptic curve, as it has no publicly known weaknesses, and is used for all Bitcoin transactions. The Bitcoin network is hugely successful and out of control, and maybe the NSA is trying to cast fear, uncertainty, and doubt (FUD) on it.

My guess is that either the NSA has been suckered by quantum computing hype like Microsoft and Google, or it wants to discourage elliptic curve cryptography because it is too secure.

Trying to apply entanglement to humanism

Marilynne Robinson writes in The Nation, an extreme left-wing magazine:

Humanism, Science, and the Radical Expansion of the Possible
Why we shouldn’t let neuroscience banish mystery from human life.

Humanism was the particular glory of the Renaissance. ...

The antidote to our gloom is to be found in contemporary science. ...

The phenomenon called quantum entanglement, relatively old as theory and thoroughly demonstrated as fact, raises fundamental questions about time and space, and therefore about causality.

Particles that are “entangled,” however distant from one another, undergo the same changes simultaneously. This fact challenges our most deeply embedded habits of thought. To try to imagine any event occurring outside the constraints of locality and sequence is difficult enough. Then there is the problem of conceiving of a universe in which the old rituals of cause and effect seem a gross inefficiency beside the elegance and sleight of hand that operate discreetly beyond the reach of all but the most rarefied scientific inference and observation. However pervasive and robust entanglement is or is not, it implies a cosmos that unfolds or emerges on principles that bear scant analogy to the universe of common sense. It is abetted in this by string theory, which adds seven unexpressed dimensions to our familiar four. And, of course, those four seem suddenly tenuous when the fundamental character of time and space is being called into question. Mathematics, ontology, and metaphysics have become one thing. Einstein’s universe seems mechanistic in comparison. Newton’s, the work of a tinkerer. If Galileo shocked the world by removing the sun from its place, so to speak, then this polyglot army of mathematicians and cosmologists who offer always new grounds for new conceptions of absolute reality should dazzle us all, freeing us at last from the circle of old Urizen’s compass. But we are not free. ...

I find the soul a valuable concept, a statement of the dignity of a human life and of the unutterable gravity of human action and experience. ...

I am content to place humankind at the center of Creation. ...

I am a theist, so my habits of mind have a particular character.

I am not trying to summarize this, or even to comment on the merits of her arguments. I just want to point out how bad physics makes its way into humanities essays.

Krauss against philosophers

Physicist Lawrence Krauss says in a interview:

Freeman Dyson, who is a brilliant physicist and a contrarian, he had pointed out based on some research — he’s 90 years old, but he had done some research over the years — I was in a meeting in Singapore with him when he pointed out that we really don’t know if gravity is a quantum theory. Electromagnetism is a quantum theory because we know there are quanta of electromagnetism called photons. Right now they’re coming, shining in my face and they’re going into the camera that’s being used to record this and we can measure photons. There are quanta associated with all of the forces of nature. If gravity is a quantum theory, then there must be quanta that are exchanged, that convey the gravitational force; we call those gravitons. They’re the quantum version of gravitational waves, the same way photons are the quantum version of electromagnetic waves. But what Freeman pointed out is that there’s no terrestrial experiment that could ever measure a single graviton. He could show that in order to build an experiment that would do that, you’d have to make the experiment so massive that it would actually collapse to form a black hole before you could make the measurement. So he said there’s no way we’re ever going to measure gravitons; there’s no way that we’ll know whether gravity is a quantum theory.

This is correct. The whole subject of quantum gravity should be considered part of theology or something else, because it is not science.

He notes that the BICEP2 tried (unsuccessfully) to find evidence of quantization of an inflaton field, a related issue.

Does physics need philosophy?

We all do philosophy and of course, scientists do philosophy. Philosophy is critical reasoning, logical reasoning, and analysis—so in that sense, of course physics needs philosophy. But does it need philosophers? That’s the question. And the answer is not so much anymore. I mean it did early on. The earlier physicists were philosophers. When the questions weren’t well defined, that’s when philosophy becomes critically important and so physics grew out of natural philosophy, but it’s grown out of it, and now there’s very little relationship between what physicists do and what even philosophers of science do. So of course physics needs philosophy; it just doesn’t need philosophers.

Philosophers have rejected XX century science, and have become more anti-science than most creationists. So asking whether physics needs philosophers is like asking whether biology needs creationists or whether astronomy needs astrologers.

Krauss was burned by a philosopher of physics who wrote a NY Times book review trashing Krauss's title, and without addressing the content of the book. Yeah, the title was overstated, but the reviewer should have been able to get past the title.

Foundation of probability theory

When physicists talk about chance, probability, and determinism, they are nearly always hopelessly confused. See, for example, the recent Delft experiment claiming to prove that nature is random.

Whether electron have some truly random behavior is a bit like talking about whether humans have free will. It certainly appears so, and there is even a relation between the concepts, and quantum mechanics leaves the possibilities open.

Randomness is tricky to define. Mathematicians have thought very carefully about the issues, and reached a XXc consensus on how to formulate it. So it is best to look at what they say.

UCLA math professor Terry Tao is teaching a class on probability theory, and this is from his introductory notes:

By default, mathematical reasoning is understood to take place in a deterministic mathematical universe. In such a universe, any given mathematical statement S (that is to say, a sentence with no free variables) is either true or false, with no intermediate truth value available. Similarly, any deterministic variable x can take on only one specific value at a time.

However, for a variety of reasons, both within pure mathematics and in the applications of mathematics to other disciplines, it is often desirable to have a rigorous mathematical framework in which one can discuss non-deterministic statements and variables – that is to say, statements which are not always true or always false, but in some intermediate state, or variables that do not take one particular value or another with definite certainty, but are again in some intermediate state. In probability theory, which is by far the most widely adopted mathematical framework to formally capture the concept of non-determinism, non-deterministic statements are referred to as events, and non-deterministic variables are referred to as random variables. In the standard foundations of probability theory, as laid out by Kolmogorov, we can then model these events and random variables by introducing a sample space (which will be given the structure of a probability space) to capture all the ambient sources of randomness; events are then modeled as measurable subsets of this sample space, and random variables are modeled as measurable functions on this sample space. (We will briefly discuss a more abstract way to set up probability theory, as well as other frameworks to capture non-determinism than classical probability theory, at the end of this set of notes; however, the rest of the course will be concerned exclusively with classical probability theory using the orthodox Kolmogorov models.)

Note carefully that sample spaces (and their attendant structures) will be used to model probabilistic concepts, rather than to actually be the concepts themselves. This distinction (a mathematical analogue of the map-territory distinction in philosophy) actually is implicit in much of modern mathematics, when we make a distinction between an abstract version of a mathematical object, and a concrete representation (or model) of that object.

Note his mention of the map-territory distinction, that I have emphasized here many times. Randomness is described by ordinary mathematical construction that look non-random. All of the formulas and theorems about randomness can be derived without any belief in true randomness. It is not clear that there is any such thing as true randomness. Randomness is a matter of interpretation.

Quantum mechanics often predicts probabilities, and physicists often say that this means that nature is random. But as you can see, mathematicians deal with probability and random variables in completely deterministic models, so probability formulas do not imply true randomness.

The Schroedinger equation is deterministic and time-reversible. And yet quantum mechanics is usually understood as indeterministic and irreversible. Is this a problem? No, not really. As you can see, mathematicians are always using deterministic formulas to model probability. These issues drive physicists like Sean M. Carroll to believe in the many-worlds interpretation (MWI), but that conclusion is entirely mistaken.