Descrying the World of Physics

Interview by Richard Marshall.

'While physics has had tremendous successes it is still an open question whether there is fundamental ontology and laws and if there is whether they can be found by the methods of physics. To the extent that this aim of physics is achieved we should be able to understand how what Sellars calls “the manifest image” emerges from fundamental physics. That is what I mean by “descrying the world in physics.”'

'Fodor, in his inimitable way, was asking why the world has this structure? That is, why there is anything except physics? Kim’s answer (over simplifying a bit) was that there is only physics. My answer (oversimplifying again) is because of physics.'

'It turns out that the Mentaculus is also a probability map and it plays a crucial role in grounding times’ arrows, counterfactuals, causation, deliberation, and compatibilist free will.'

'Steinhardt (one of the original developers of Inflation) noticed that the multiverse undermines the alleged explanatory and predictive success of the original proposal. If the multiverse is truly a consequence of inflation then the theory undermines itself.'

Barry Loewermoved to Rutgers in 1989 and has been chair and grad director. He teaches courses and seminars in philosophy of science and philosophical logic. Here he discusses his project descrying the world of physics, how he answers Fodor's question 'why is there more than physics?, materialism, consciousness, the direction of time, the behaviours of micro and macro states, the Mentaculus, why he prefers Boltzman's realism to anti-realism, freewill, the status of probabilities used in physics, comparing Lewis's possible worlds with Everett's many worlds, and the philosophical challenges of cosmological inflation. Big Bang Bomb!!!

3:AM:What made you become a philosopher?

Barry Loewer:When I was a freshman at Amherst College I took a history course about the causes of WWI and became puzzled about what it is for one event to cause another. When I asked the professor about this he said that it is the job of philosophy to answer questions like this and sent me to Professor Joe Epstein who was a really great teacher and he got me on a project that I have been interested in ever since.

3:AM:You’re currently working in the philosophy of cosmology and metaphysics. One aspect of this you’ve been working with is a project you’ve labelled ‘descrying the world of physics’? Can you tell us what this is and why it is so interesting?

BL:Physics aims to provide an account of the world’s fundamental ontology and laws. While physics has had tremendous successes it is still an open question whether there is fundamental ontology and laws and if there is whether they can be found by the methods of physics. To the extent that this aim of physics is achieved we should be able to understand how what Sellars calls “the manifest image” emerges from fundamental physics. That is what I mean by “descrying the world in physics.”

3:AM:So Jerry Fodorasked why is there anything except physics? He was responding to Jaegwon Kim’s views about the relationship between the special sciences and physics. First could you sketch for us what Kim was arguing and what Fodor’s question was challenging?

BL:In his famous paper Special Sciences(Or: The Disunity of Science as a Working Hypothesis) Fodor attempted to spell out an account of the relationship between a special science like psychology and more fundamental (and ultimately the most fundamental science- physics) that endorsed both the idea that special science laws and causation are autonomous from but also grounded in the laws and causation of the more fundamental science. Fodorargued that there are laws that connect properties of the higher level science that a multiply realized by properties in the more fundamental science that themselves are connected by laws that implement the higher level laws. Fodor, in his inimitable way, was asking why the world has this structure? That is, why there is anything except physics? Kim’s answer (over simplifying a bit) was that there is only physics. My answer (oversimplifying again) is because of physics.

3:AM:Why don’t you think Fodor’s proposed response to Kim works?

BL:Mainly because Fodor has a mistaken view about the structure of the laws of physics and more specifically because he neglects the probabilistic structure of the world that derives from statistical mechanics and the dynamical laws.

3:AM:Materialism was once claimed to be natural metaphysics within the bounds of science. It was a position that depended on science telling us that the world is made of matter. Science doesn’t tell us that now does it, so for many physicalism has replaced materialism. What’s the difference between materialism and physicalism and why has physicalism appealed to so many?

BL:Materialism is the view that every object in space-time is composed of matter. As science developed it also included the idea that there are a limited number of kinds of matter- molecules of various kinds- which themselves are composed of atoms of around 100 kinds which are themselves composed of protons, neutrons, electrons etc.

3:AM:I guess this issue gets to the heart of your descrying project: how do we get mentality, consciousness and intentionality, normativity, rationality, ethics, aesthetics, free will, colours, sounds, times arrow, causation and nomological counterfactuals from physics? Consciousness is famously a hard problem, but you raise time’s arrow as a hard problem for physics don’t you? Can you sketch out why the fundamental dynamical laws and the second law of thermodynamics create a hard problem?

BL:Consciousnessis indeed a hard problem. I think that some progress has made there by proponents of the “phenomenal concept strategy” proposed by by Brain Loar and developed by, among others, my wife Katalin Balog.

The direction of time is an easier problem at least as far as physical processes are concerned. Almost all macroscopic processes exhibit a temporal directionality; e.g. ice in warm water melts, we are born as babies and grow to adults and then die, we can influence events in one temporal direction (what we call “the future”) but not in the other temporal direction (“the past”), we have records (including memories) of the past but not the future, and so on. The problem for descrying the world in physics is that the fundamental dynamical laws have a kind of temporal symmetry wrt macroscopic processes. For every temporal sequence of particle and field configurations that compose a macroscopic process that is compatible with the dynamical laws (say the melting of ice) the temporally reverse process (the spontaneous forming of a block of ice out of warm water) is also compatible with the dynamical laws. But we never see the temporally reverse processes. Why is that? Ludwig Boltzmann partly answered this question. He was wondering why all macroscopic processes conform to the second law of thermodynamics which, in its initial formulation, says that the entropy of an isolated system never decreases and typically increases.

The entropy of a macroscopic system corresponds to the number (or measure) of micro states that realize its macro state. Boltzmann posited a probability distribution over micro states that has the consequence that the entropy of a macro system will very likely increase in the future and so thought he answered his question. Unfortunately this proposal has the consequence that entropy was greater in the past as well as the future. This is called “the reversibility problem.” The solution, which was already suggested by Boltzmann and latter by Eddington, Feynman, Penrose and others is to posit that the entropy of the universe was very small at the time immediately after the big bang. This is a cosmological hypothesis that David Albert has dubbed “The Past Hypothesis.” It is perhaps suprising that the facts that ice cubes typically melt but don’t spontaneously appear, that eggs cook and don’t uncook, and so on are explained by a cosmological hypothesis. David and I call the package consisting of the fundamental dynamical laws, the Boltzmann probability distribution, and the Past Hypothesis “The Mentaculus.” The word comes from an amusing scene in the Coen brothers film A Serious Manin which a character calls a a book he is obsessively working on “The Mentaculus” and explains that it is a probability map of the world. The key idea is that adding the probability distribution and the Past Hypothesis to the dynamical laws enables one to see how macroscopic regularities are grounded in micro physical processes. Even application of dynamical laws to macro processes like the motions of planets and the tides require these additions if we take seriously that all macro phenomena are composed of micro phenomena. It turns out that the Mentaculus is also a probability map and it plays a crucial role in grounding times’ arrows, counterfactuals, causation, deliberation, and compatibilist free will.

3:AM:Another hard problem you identify concerns the behaviors of micro and macro states. Again, what’s the problem here that makes it hard for physics?

BL: The vast difference in scale- a macroscopic object consists of something on the order of 10 to the 23 micro particles makes it hard to produce a detailed explanation of macro behavior in terms of micro behavior very difficult in general. But there are certain macro regularities that are more easily explainable in micro terms involving the fundamental dynamics together with the Boltzmann probability distribution and the Past Hypothesis, aka the Mentaculus; for example, the second law of thermodynamics, why we have records of the past, and so on. The Mentaculus doesn’t assume a direction of time but rather explains the asymmetry of temporal processes and so the distinction between past and future. The “Past Hypothesis” earns its name because of this asymmetry.

[Boltzmann]

3:AM:Why aren’t you content with an anti-realist position towards these things, as adopted by Mach? Why go with Boltzmann’s realism? Isn’t it the realism that makes the hard problem hard?

BL:Boltzmann’s realism re atoms has been enormously successful. When Richard Feynman was asked to think of a single sentence that would convey the most important scientific knowledge we possess, he answered simply: "Everything is made of atoms." Anti-realist views treat science like an instruction manual for how to make predictions. I had one of these manuals for a car I used to own. But it gave no insight into how the car really worked so when something went very wrong I wasn’t able to figure out what to do. I am a realist because I would like to know how the world works and I think the various sciences make the best proposals for how things really work.

3:AM:The hard problem of freewill you characterize in terms of influence and control don’t you? If determinism in micro physics is true and we have an influence then don’t we have an influence on the past as well as the future – which seems wrong? How does your Mentaculus device help, and are we left with a robust realist view of freewill or is it just a myth?

BL:Yes…given determinism (as we have been assuming throughout this discussion) there is a correlation between the decisions a person makes (which I assume correspond to certain physical processes) and the physical history back to the time of the past hypothesis. However, because of the asymmetry that is built into the correlations grounded by the Mentaculus and the structure of our brains these correlations are unknown to us and are not useful to us. On the other hand the correlations between decisions and circumstances in the temporal direction away from the past hypothesis (what we call “the future”.) are knowable and very useful to us. The details and defense of this account are complicated and I can’t fully develop them here. The account doesn’t endorse what philosophers call “libertarian free will” but it does explain why we think we have libertarian free will even though it is a myth.

3:AM:So are probabilities used in physics objective or subjective?

BL:My view is that probabilities in physics (for example in the Mentaculus and in Quantum mechanics) should be understood as objective probabilities. The account that I think is the best account of objective probabilities is David Lewis’ Best Systems Account of laws and probabilities. One place where I disagree with Lewis is that he thought that non-trivial objective physical probabilities require that the dynamical laws are not deterministic. I have argued in a number of papers that an account much like Lewis’ extends to the probabilities that occur in theories with deterministic dynamical laws e.g. the Mentaculus and in deterministic version of Quantum Mechanics. I very much like Lewis’ account of laws which is Humean in inspiration and opposed to more metaphysical accounts due to Armstrong, Maudlin, and advocates of powers like Bird and Cartwright. I like Lewis’ account because it is free of the metaphysical commitments- which I think ultimately are theological in origin- of some competing accounts and because of the ways it fits in with scientific methodology. But this is a long story.

3:AM:Everettians look at probabilities in a way that sounds a bit like a metaphysical version of David Lewis’s possible worlds, which are used in semantics and modal logic. Presumably they clash somewhere along the line, and so presumably if this is right then modal realism is false. How do you respond to this sort of thinking? How should we understand Everett’s many worlds, and is it the best way of thinking about quantum physics?

BL:There are some philosophers who have proposed that Lewis’ possible worlds and Everett’s many worlds are the same. But this isn’t correct. For Lewis worlds are arrangements of perfectly natural properties in space-times that are causally isolated from one another. They are the fundamental elements of concrete reality. Worlds must be metaphysically possible but may have laws that differ from the laws of what we call the actual world. The worlds in Everett’s account of quantum mechanics correspond to decoherent branches of the actual world’s universal quantum wave function. They must obey the laws of quantum mechanics (so some metaphysical possibilities are excluded), they are not fundamental, and they are not causally isolated from each other since, depending on the fundamental quantum mechanical law worlds may recohere and interfere (as in a two slit experiment). I think Everett’s account is immensely interesting and important but I think it faces an insuperable problem making sense of quantum mechanical probabilities. Advocates of Everett’s account have been working on this problem and some (e.g. David Wallace, Sean Carroll) think they have solved it but I don’t agree. I don’t know what the correct account of quantum mechanics is but I think the best account around are versions of Bohm’s account (often misnamed a “hidden variable” account) developed by John Bell and Shelly Goldstein and his group.

3:AM:Inflation when used in physics raises some interesting philosophical problems, one being that it seems to predict that whatever could happen will happen, which in turn raises the problem that it’s a theory that can’t have empirical evidence for it. Can you sketch out the issue and then say something about whether you think it’s ok for scientific theories to be beyond the bounds of empirical evidence? On the face of it, it seems to be doing what scientists have sometimes criticized metaphysicians of doing – just speculating?

BL:Cosmology is full of issues that should interest philosophers. Inflation is an account (originally proposed by Alan Guth and then modified and fixed up by Andre Linde and Paul Steinhardt and Andreas Albrecht) of the very early universe according to which the universe expanded at an accelerating rate doubling every 10 to the minus 38 seconds or so for a very short amount of time. This period of accelerated expansion, as Guth says, put the “bang into the big bang.” The subsequent expansion of the universe discovered by Hubble is a kind of coasting after this initial impulse (However the picture was complicated by the discover in 1998 that there is still some accelerated expansion though at a very much smaller rate that corresponds to a cosmological constant in equations of GR that describe the expansion of the universe). Guth claimed and most of the community of cosmologists agreed that his proposal explained certain features of the universe; for example why the spatial geometry of the universe is Euclidian, why the early universe was almost perfectly homogenous but not quite perfectly homogenous thus allowing for the formation of stars, galaxies and so on.

Shortly after its proposal cosmologists mostly came to think that inflation would produce not just the observable universe but many other universes as well. Further these other universes could have different physical features from the observable universe e.g. different geometries, may not be homogeneous, maybe different kinds of fundamental fields and particles. Alan Guth summed this up by saying that inflation produces universes so that anything that can happen does happen in some universe or other. So this is another many universes proposal though different from Lewis’ and Everett’s (though there are some who try to identify one of these with another one of these). Some physicists welcomed this consequence – the multiverse- thinking that it provided the universes that could be appealed to in explanations of why certain features of our universe seem to be fine-tuned for the existence of life. For example, Steven Weinberg suggested that the surprisingly small value of the cosmological constant that describes the current accelerated expansion could be explain anthropically by proposing that universes with all possible values are generated by inflation but only those with small values can support life. But Steinhardt (one of the original developers of Inflation) noticed that the multiverse undermines the alleged explanatory and predictive success of the original proposal. If the multiverse is truly a consequence of inflation then the theory undermines itself. Recently an article in The Scientific American(Feb 2017) by Ijjas, Loeb, and Steinhardt created a kerfuffle in the cosmology community by developing this and other criticisms of inflation. In response a number of cosmologists and physics wrote a letter defending inflation. Since many of the issues intersect with philosophical issues about evidence and the nature of scientific methodology this is a very exciting flied for philosophers of science.

3:AM:And finally, are there five books that you could recommend to us that will take us further into your philosophical world?

BL:I am incredibly fortunate to be at Rutgers and having as friends incredibly creative philosophers who live nearby. They are among the authors of books that are really important to me

1. David Albert Quantum Mechanics and Experience and his Time and Chance

2. Tim Maudlin Quantum Non-locality and Relativityand his

The Metaphysics within Physics

3. Jenann Ismael How Physics Makes Us Free

4. Sean CarrollFrom Eternity to Here

5. David Chalmers The Conscious Mind

ABOUT THE INTERVIEWER
Richard Marshallis still biding his time.

Buy his new book hereor his first book hereto keep him biding!