Category Archives: Science

Are predictions an essential part of science?

Theoretical physicist Sabine Hossenfelder recently wrote that that “predictions are over-rated” and that one should instead judge the merits of scientific models “by how much data they have been able to describe well, and how many assumptions were needed for this”, finishing with the suggestion that “the world would be a better place if scientists talked less about predictions and more about explanatory power”.

Others disagreed, including philosopher-of-science Massimo Pigliucci who insists that “it’s the combination of explanatory power and the power of making novel, ideally unexpected, and empirically verifiable predictions” that decides whether a scientific theory is a good one. Neither predictions nor explanatory powers, he adds, are sufficient alone, and “both are necessary” for a good scientific theory.

Popper’s criterion of falsification (the possibility that a theory’s predictions can be empirically refuted) is, of course, one of few elements of the philosophy of science to have attained widespread awareness. But is Popper’s maxim descriptive or prescriptive? If it merely describes what scientists tend to do, then, if scientists came to feel that predictions were not so crucial, would their enterprise still be “science”? Or, if the maxim is prescriptive, such that falsification is a necessary part of the scientific method, then by what authority is that prescription established?

To answer that, let’s turn to Feynman’s well known summation of science:

The first principle is that you must not fool yourself — and you are the easiest person to fool.

Scientists do their best to construct the best and truest model of the world. Pseudoscientists have fooled themselves into a false understanding of the world. And it’s easy to do that, because, given a set of facts, anyone can construct a story that weaves those facts into an overall picture that the story-teller wants to be true. They may need any number of ad hoc explanations, but humans are good at that. It’s easy to sustain the belief that, say, God always answers prayer, if you allow yourself wide flexibility about what the answer looks like, including “God said no this time”.

So both Hossenfelder and Pigliucci are right: a good scientific theory needs to explain the maximum amount of data with the minimum number of ad hoc features. But predictions really are the acid test. If you are making predictions about things where you don’t already know the answer, then your ad hoc explanations will prove useless and sterile. Only an accurate theory — one that correctly describes aspects of the world — will be able to reliably generate predictions that turn out true. This is why making predictions about things you don’t know, and then attempting to verify them, is the gold-standard method that all scientists should adopt when they can, to check whether they have fooled themselves. The telling give-away of the pseudoscientist is their reluctance to submit to that test.

But making predictions that can then be verified may not always be possible. Yes, the scientific method asks that such be done where it can be, but what if we’re talking about topics where the time required or the energy required are not possible? Need we conclude that such topics are beyond the domain of science?

Let’s take a concrete example. Given the finite age of the universe and the finite speed of light (and hence the finite speed at which information can travel from one region of space to another), we can never obtain information about the universe beyond an “observable horizon”, and thus can never empirically verify statements about such a region. Does that mean that any statement about such regions is outside science (perhaps being metaphysical or pseudoscientific)?

A further example concerns attempts to describe the physics of the Planck scale, which is relevant to attempts to find a unified description of the forces of nature, or to understand the origins of the Big Bang, yet which is orders of magnitude beyond our ability to recreate in particle accelerators. Is any such quest pseudoscience? And if it is, how far beyond our current ability to test is it permissible for scientists to construct theories? It would be weird to suggest that a factor 2 is acceptable, but a factor 10 not.

I prefer to fall back on Feynman’s dictum. If we’re discussing topics beyond our ability to test predictions then we need to be extra careful not to fool ourselves, since we won’t have the gold-standard test. But then in science we have to make do with the tools we have; neither cosmologists nor paleontologists can replicate findings in laboratory experiments, yet those fields are still sciences, despite what school textbooks might say about “the scientific method” and the requirement to replicate experiments.

We should see verifying predictions as similar to replicating experiments under laboratory conditions — yes scientists should do it where they can, as being the best ways of minimising self-fooling, but in the end science is pragmatic and often has to make do. Thus there is nothing unscientific about trying to understand aspects of the universe that we cannot directly test, one just has to be extra cautious in the claims one makes. A statement such as: “As far as we know, the universe continues much the same beyond the observable horizon” would seem to be a reasonable feature of a cosmological model, even though it is beyond empirical testing.

So, overall, predictions are not over-rated, but nor are they fully essential. I think this lands me roughly midway between Hossenfelder and Pigliucci.

Science Unlimited, Part Three: Philosophy

This is the Third Part of a review of Science Unlimited? The Challenges of Scientism, edited by Maarten Boudry and Massimo Pigliucci. See also Part 1, focusing on pseudoscience, and Part 2, focusing on the humanities.

Science started out as “natural philosophy” until Whewell coined the newer name “science”. As a scientist I have a PhD and am thus a “Doctor of Philosophy”. And yet many philosophers assert that today “philosophy” is an enterprise that is distinct from “science”.

The argument runs that philosophy is about exploration of concepts, and what can be deduced purely by thinking about concepts, whereas science is heavily empirical, rooted in observation of the world. Thus philosophy (exploration of concepts) and science (empirical observation) are fundamentally different beasts. And both are necessary for a proper understanding.

But, for this distinction to hold, a necessary corrollary is that science does not involve exploration of concepts, and concerns itself only with the accumulation of observation. Yet to me that is an utterly impoverished view of science, and one that is untenable. In order to advance understanding we need both the exploration of concepts and the guidance of empirical observation — either on its own won’t get far. Accumulating observations by itself is mere “stamp collecting” (to quote a derogatory remark that physicists aim at anyone not paying sufficient attention to explanations and understanding). As philosophers themselves know, all observation is “theory laden” in that one cannot even assimilate observational evidence without equal attention to what it means.

In essence, science is a continual process of revising and improving a “web of ideas” that contains our understanding of the world. We continually test the web by comparing its outputs to empirical data, looking for any mismatch, and then trying to figure out the best way of adjusting the web in order to eliminate the anomaly. It follows that attention to the internal coherence of the web of ideas, and exploring the implications of the ideas — and thus analysis of concepts — is a vital and basic part of the overall scientific enterprise.

The two halves of the whole are perhaps most clearly seen in physics, where practitioners are divided into “theoretical physicists”, who spend their lives exploring the implications of ideas and trying to scheme up better ones, and “observers” and “experimentalists” who concentrate on adding to the pile of empirical data that tests the concepts. Obviously this only works if the two halves are continually talking to each other, and so everyone sees themselves as part of the same overall enterprise, specialising in one “style” of science because division of labour allows the focused expertise necessary to make progress.

To me as a physicist, it makes little sense to read that some philosophers think that exploring ideas and concepts for their own sake is a philosophical activity that is “not science” and is clearly distinct from science. So why is it then defended by some philosophers? I suggest that the reason is sociological. Science nowadays is such a juggernaut that adjacent disciplines fear being trampled underfoot, and so jostle to establish a bailiwick of their own from which science is excluded. While understandable, such a path could lead to irrelevance.

Philosophy, with its role of asking certain types of question, is better thought of, not as distinct from science, but as a style of doing science, in the broadest sense of “science” as increasing our understanding of the world. Other “styles” of science, in addition to theoretical analysis, include accumulating observations, designing and performing experiments, and modelling a situation on a computer. The best approach is to combine and synthesize all of these styles. None of them would get us far on its own, and they best succeed in harmony with the others. Philosophy, therefore, is best done in close conjunction with adjacent disciplines, such as the sciences, and could condemn itself to pointless meanderings if it forgets that.

As expected, the authors in Science Unlimited have a spread of views on this issue. Maarten Boudry is closest to my own view, arguing against those of his colleagues who “still regard philosophy as independent from and conceptually prior to science”, and saying instead that: “much of philosophy is now tightly ensnared in the web of knowledge. Philosophy of mind shades into cognitive science, neurology, and linguistics. Epistemology is intertwined with cognitive psychology and evolutionary biology”, while declaring — correctly — that the sciences “often deal with conceptual issues that can be characterized as broadly `philosophical’ in nature”.

Stephen Law, however, is less sympathetic to this view, saying: “philosophical questions are, for the most part, conceptual rather than scientific or empirical”, and that: “in order to solve many classic philosophical problems, we’ll need to retire to the armchair, not to the lab”.

But, equally, theoretical physicists don’t work with laboratory equipment, taking measurements, they work with ideas and concepts. The internal coherence of concepts about the world is just as much a concern for scientists as for philosophers.

A current example is the black-hole information paradox, where the paradox is that current models of black holes suggest that “information” (which itself is a highly abstract concept, not a direct observable) is destroyed when material falls into a black hole. And yet, a basic principle of quantum mechanics (the best theory of matter, thought to apply everywhere) says that information can never be destroyed. Trying to resolve the inconsistency is currently exercising many of the world’s top theoretical physicists, partly because the solution might point the way to a model of “quantum gravity”, the long-sought unification of quantum mechanics with general relativity. Yet this activity is entirely conceptual, since observations and experiments pertaining directly to the issue are way beyond current capabilities. Physicists still regard the enquiry as “scientific”, even if some philosophers might want to declare it to be “metaphysics”.

Stephen Law’s own example is Galileo’s thought experiment of dropping balls from the top of the Leaning Tower of Pisa. The thought experiment demonstrates that balls of different weights must fall at the same speed, else one arrives at a contradiction. Law asks: “Is Galileo’s thought experiment an example of science, or of philosophy?” Since it “targets a scientific theory”, about how physical objects behave, “perhaps it belongs more properly to science”, but, Law continues, “the same armchair method employed by Galileo is also regularly employed by philosophers”.

And just as often by scientists. And so both science and philosophy are about concepts, and there is no clear demarcation between them. Such a view is also advocated by Mariam Thalos, who writes: “I propose to use the label science for all of what Aristotle would have called knowledge. Hence it applies to anything that accepts the authority of a coherent set of standards that aim at truth. […] Thus, philosophy is a science”.

In contrast, Massimo Pigliucci attempts to draw clear distinctions between philosophy and science, boldly declaring:

I would go as far as to challenge my scientistically inclined colleagues who contributed to this volume to show me a single instance of systematic observation or experiment (i.e., an example of science) throughout this collection of essays. The contributions Maarten and I collected here are so inherently philosophical in nature that they stand as a self-evidence refuation that science is our only path to knowledge and understanding.

Here, Pigliucci explicitly limits science to: “systematic observation or experiment”, overlooking the entire conceptual, theoretical and model-building side of science. Yes, if you limit science to only that aspect, then that impoverished and neutered hemi-science would be inadequate on its own. You do indeed need all the different styles, working in concert, to do the best science, and that includes the conceptual analysis characteristic of Boudry & Pigliucci’s book of essays.

Pigliucci replies that such a broad conception of science amounts to: “redefining science in a way that is coextensive with reason itself, which is not only historically and factually grossly inaccurate but ultimately meaningless”.

But I deny that it is meaningless, instead it points to a consilience that is a necessary part of seeking out knowledge. None of the “styles” succeeds on its own. One cannot define science as being limited to “systematic observation or experiment” while excluding the conceptual and model-building side of science that is needed to interpret the observations and experiments; such a science would not function.

Philosophers themselves agree with this, pointing to the inevitably “theory-laden” nature of even simple observations. The Quinean-web view of science — with a constant iteration between observation and experiment, on the one hand, and a “web of ideas” on the other — demands that science be just as much about the “web of ideas” as about the observation and experiment. Thus I would go as far as suggesting that Pigliucci’s attempted demarcation between philosophy and science is not consistent with the nature of science and not consistent with the best philosophical understanding of science.

Part 4: Reductionism

Science Unlimited, Part One: Pseudoscience

Philosophers Maarten Boudry and Massimo Pigliucci have recently edited a volume of essays on the theme of scientism. The contributions to Science Unlimited? The Challenges of Scientism range from sympathetic to scientism to highly critical.

I’m aiming to write a series of blog posts reviewing the book, organised by major themes, though knowing me the “reviewing” task is likely to play second fiddle to arguing in favour of scientism.

Of course the term “scientism” was invented as a pejorative and so has been used with a range of meanings, many of them strawmen, but from the chapters of the book emerges a fairly coherent account of a “scientism” that many would adopt and defend.

This brand of scientism is a thesis about epistemology, asserting that the ways by which we find things out form a coherent and unified whole, and rejecting the idea that knowledge is divided into distinct domains, each with a different “way of knowing”. The best knowledge and understanding is produced by combining and synthesizing different approaches and disciplines, asserting that they must mesh seamlessly. Continue reading

The cosmological multiverse and falsifiability in science

The cosmological “multiverse” model talks about regions far beyond the observable portion of our universe (set by the finite light-travel distance given the finite time since the Big Bang). Critics thus complain that it is “unfalsifiable”, and so not science. Indeed, philosopher Massimo Pigliucci states that instead: “… the notion of a multiverse should be classed as scientifically-informed metaphysics”.

Sean Carroll has recently posted an article defending the multiverse as scientific (arXiv paper; blog post). We’re discussing here the cosmological multiverse — the term “multiverse” is also used for concepts arising from string theory and from the many-worlds interpretation of quantum mechanics, but the arguments for and against those are rather different. Continue reading

How not to defend humanistic reasoning

Sometimes the attitudes of philosophers towards science baffle me. A good example is the article Defending Humanistic Reasoning by Paul Giladi, Alexis Papazoglou and Giuseppina D’Oro, recently in Philosophy Now.

Why did Caesar cross the Rubicon? Because of his leg movements? Or because he wanted to assert his authority in Rome over his rivals? When we seek to interpret the actions of Caesar and Socrates, and ask what reasons they had for acting so, we do not usually want their actions to be explained as we might explain the rise of the tides or the motion of the planets; that is, as physical events dictated by natural laws. […]

The two varieties of explanation appear to compete, because both give rival explanations of the same action. But there is a way in which scientific explanations such as bodily movements and humanistic explanations such as motives and goals need not compete.

This treats “science” as though it stops where humans start. Science can deal with the world as it was before humans evolved, but at some point humans came along and — for unstated reasons — humans are outside the scope of science. This might be how some philosophers see things but the notion is totally alien to science. Humans are natural products of a natural world, and are just as much a part of what science can study as anything else.

Yes of course we want explanations of Caesar’s acts in terms of “motivations and goals” rather than physiology alone — is there even one person anywhere who would deny that? But nothing about human motivations and goals is outside the proper domain of science. Continue reading

Another philosopher of science doesn’t understand science

Maybe I’m having a philosopher-bashing week. After disagreeing with Susan Haack’s account of science I then came across an article in the TLS by David Papineau, philosopher of science at King’s College London. He does a good job of persuading me that many philosophers of science don’t know much about science. After all, their “day job” is not studying science itself, but rather studying and responding to the writings of other philosophers of science. Continue reading

Science is a product of science!

The latest issue of Free Enquiry magazine contains several articles about philosophy and science, including an article by Susan Haack, a philosopher of science who “defends scientific inquiry from the moderate viewpoint”, rejecting cynical views that dismiss science as a mere social construction, but also rejecting “scientism”.

While Susan Haack talks quite a bit of sense about science, she promotes a view that is common among philosophers of science but which I see as fundamentally wrong. That is the idea that science and the scientific method depend on philosophical principles that cannot be justified by science, but instead need to be justified by philosophy. Continue reading

Attorney General Jeff Sessions scores 8 out of 20 on Religious Freedom

The US attorney general, Jeff Sessions, has issued a memo directing government bodies on how to interpret religious freedom. Unfortunately Sessions misinterprets religious liberty as granting religious people greater rights than the non-religious have. This is a violation of the deeper principle of treating all citizens equally, regardless of their religious views.

Viewed from the stance of equality we can properly understand religious freedom as a form of free speech. That is, you may espouse your religious views, and if you have a general right to do something you may do that same thing with added religious content. Further, the state may not treat you any less favourably owing to that religious content, but nor may it treat you more favourably.

From that perspective, let’s score Sessions’s memo, in which he declares 20 “principles of religious liberty”. Continue reading

Should Nobel Prizes go to teams?

The 2017 Nobel Prize for Physics has gone to members of the LIGO consortium for the detection of gravitational waves, namely to Rainer Weiss, Kip Thorne and Barry Barish. But the contributions of many hundreds of people were necessary for the success of LIGO and so it can be argued that the restriction to three people is wrong and that future Nobel Prizes should go to teams.

Professor Martin Rees, the Astronomer Royal, told BBC correspondent Pallab Gosh that: “LIGO’s success was owed to hundreds of researchers. The fact that the Nobel Prize committee refuses to make group awards is causing increasingly frequent problems and giving a misleading impression of how a lot of science is actually done”.

Rees is right, of course, but would changing it be a good thing? It would mean that nearly all future Nobels in physics would go to teams, either simply to a named team or to a list of team members that could amount to hundreds.

I’m not sure this would be a good change. Continue reading

Fundamental ontology: what is the universe actually made of?

In his classic “Feynman lectures on physics”, Richard Feynman starts by saying:

If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generation of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis that all things are made of atoms — little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another.

Of course atoms are not the basic unit, they are composed of nuclei surrounded by electrons. The nuclei are then composed of protons and neutrons (and short-lived virtual particles such as pions), and the protons and neutrons are themselves composed of quarks and gluons.

But what is the ultimate level? What, when one goes down to the most fundamental level, are things made of? While there are lots of opinions there is no accepted answer, and mulling it over for myself I realised that none of the options are attractive in the sense of aligning with intuition about what “physical stuff” would be made of. Here are some of the possibilities: Continue reading