William M. Briggs

Statistician to the Stars!

Author: Briggs (page 3 of 416)

Yet Another Author Claims Statistically Significant Temperature Change. 99.999%!

Statistical significance is even uglier than this painting, which is pretty darn ugly.

Statistical significance is even uglier than this painting, which is pretty darn ugly.

Update 6 Sep 2014 Yet another another another study has claimed “statistical significance”, this one by Philip Kokica, Steven Crimpc, and Mark Howdend. “A probabilistic analysis of human influence on recent record global mean temperature changes.” I haven’t had a chance to look at that study in any detail yet, but I imagine many of the remarks below hold. If I find the new paper needs a new post, I’ll do one in the future.

Update 12 Apr 2014 This originally ran 28 May 2013, but given Shaun Lovejoy’s latest effort in Climate Dynamics to square the statistical circle, it’s necessary to reissue. See the Lovejoy update at the bottom.

My Personal Consensus

I, a professional statistician, PhD certified from one of the top universities in the land—nay, the world—a man of over twenty years hard-bitten numerical experience, a published researcher in the very Journal of Climate, have determined that global temperatures have significantly declined.

You read that right: what has gone up has come back down, and significantly. Statistically significantly. Temperatures, he said again, have plunged significantly.

This is so important a scientific result that it bears repeating. And there is another reason for a recapitulation: I don’t believe that you believe me. There may be a few of you who are suspicious that old Briggs, well known for his internet hilarity, might be trying to pull a fast one. I neither josh nor jest.

Anyway, it is true. Global warming, by dint of a wee p-value, has been refuted.

Which is to say that according to my real, genuine, mathematically legitimate, scientifically fabricated scientific statistical scientific model (calculated on a computer), I was able to produce statistical significance and reject the “null” hypothesis of no cooling. Therefore there has been cooling. And since cooling is the opposite of warming, there is no more global warming. Quod ipso facto. Or something.

I was led to this result because many (many) readers alerted me to a fellow named Lord Donoughue, who asked Parliament a question which produced the answer that “the temperature rise since about 1880 is statistically significant.” Is this right?

Not according to my model. So who’s model, the Met Office’s or mine, is right?

Well, that’s the beauty of statistics. Neither model has to be right; plus, anybody can create their own.

Statistical model

Here’s the recipe. Grab, off the shelf or concoct your own with sweat and integrals, a model. The more scientific sounding the better. Walk into a party with “Autoregressive heteroscedastic GARCH process” or “Coupled GCM with Kalman-filtering cloud parameterization” on your lips and you simply cannot fail to be a hit.

Don’t despair of finding a model. They are as dollars to a bureaucracy: they are infinite! Thing is, all models, as long as they are not fully deterministic, have some uncertainty in them. This uncertainty is parameterized by a lot of knobs and switches which can be throw into any number of configurations.

Statistical “significance” works by tossing some data at your model and hoping that, via one of a multitude of mathematical incantations, one of these many parameters turns out to be associated with a wee p-value (defined as less than the magic number; only adepts know this figure, so if you don’t already have it, I cannot tell you).

If you don’t get a wee p-value the first time, you keep the model but change the incantation. There are several, which practically guarantees you’ll find joy. Statisticians call this process “hypothesis testing.” But you can think of it as providing “proof” that your hypothesis is true.

Funny thing about statistics is that you can always find a model with just the right the set of parameters so that one, in the presence of data, is associated with a wee p-value. This is why, for example, one scientist will report that chocolate is good for your ticker, while another will claim chocolate is “linked to” heart disease. Both argue from a different statistical model.

Same thing holds in global warming. One model will “confirm” there has been statistically significant cooling, another will say statistically significant warming.

Say What?

The global temperature (as measured operationally) has certainly changed since the 1800s. Something, or some things, caused it to change. It is impossible—as in impossible—that the cause was “natural random variation”, “chance” or anything like that. Chance and randomness are not causes; they are not real, not physical entities, and therefore cannot be causes.

They are instead measures of our ignorance. All physical and probability models (or their combinations) are encapsulations of our knowledge; they quantify the certainty and uncertainty that temperature takes the values it does. Models are uncertainty engines.

This includes physical and statistical models, GCMs and GARCHes. The only difference between the two is that the physical models ties our uncertainty of temperatures to knowledge of other physical processes, while statistical models wed uncertainty to mysterious math and parameterizations.

A dirty, actually filthy, open secret in statistics is that for any set of data you can always find a model which fits that data arbitrarily close. Finding “statistical significance” is as difficult as the San Francisco City Council discovering something new to ban. The only evidence weaker than hypothesis tests are raw assertions and fallacies of appeal to authority.

The exclusive, or lone, or only, or single, solitary, sole way to check whether any model is good is if it can skillfully predict new data, where “new” means as yet unknown to the model in any way—as in in any way. The reason skeptics exist is because no know model has been able to do this with temperatures past a couple of months ahead.

The Dramatic Conclusion

There isn’t a soul alive or dead who doesn’t acknowledge that temperatures have changed. Since it cannot be that the observed changes are due to “natural variation” or “chance,” that means something real and physical, possible many different real and physical things, have caused temperature to take the values it did.

If we seek to understand this physics, it’s not likely that statistics will play much of role. Thus, climate modelers have the right instinct by thinking thermodynamically. But this goes both directions. If we have a working physical model (by “working” I mean “that which makes skillful predictions”) there is no reason in the world to point to “statistical significance” to claim temperatures in this period are greater than temperatures in that period.

Why abandon the physical model and switch to statistics to claim significance when we know that any fool can find a model which is “significant”, even models which “prove” temperatures have declined? This is nonsensical as it is suspicious. Skeptics see this shift of proof and rightly speculate that the physics aren’t as solid as claimed.

If a statistical model has skillfully predicted new temperatures, and of course this is possible, then it is rational to trust the model to continue to do so (for the near horizon; who trusts a statistics model for a century hence?). But there is not a lot that can be learned from the model about the physics, unless the parameters of the model can be married to physical concepts. And if we can do that, we should be able to create skillful physical models. Good statistical models of physical processes thus work toward their own retirement.

Ready for the punch line? It is shocking and deeply perplexing why anybody would point to statistical significance to claim that temperatures have gone up, down, or wiggled about. If we really want to know whether temperatures have increased, then just look. Logic demands that if they have gone up, then they have gone up. Logic also proves that if they have gone down, then they have gone down. Statistical significance is an absurd addition to absolute certainty.

The only questions we have left are—not whether there have been changes—but why these changes occurred and what the changes will be in the future.

Lovejoy Update To show you how low climatological discourse has sunk, in the new paper in Climate Dynamics Shaun Lovejoy (a name which we are now entitled to doubt) wrote out a trivially simple model of global temperature change and after which inserted the parenthetical words “skeptics may be assured that this hypothesis will be tested and indeed quantified in the following analysis”. In published comments he also fixated on the word “deniers.” If there is anybody left who says climate science is no different than politics, raise his hand. Anybody? Anybody?

His model, which is frankly absurd, is to say the change in global temperatures is a straight linear combination of the change in “anthropogenic contributions” to temperature plus the change in “natural variability” of temperature plus the change in “measurement error” of temperature. (Hilariously, he claims measurement error is of the order +/- 0.03 degrees Celsius; yes, three-hundredths of a degree: I despair, I despair.)

His conclusion is to “reject”, at the gosh-oh-gee level of 99.9%, that the change of “anthropogenic contributions” to temperature is 0.

Can you see it? The gross error, I mean. His model assumes the changes in “anthropogenic contributions” to temperature and then he had to supply those changes via the data he used (fossil fuel use was implanted as a proxy for actual temperature change; I weep, I weep). Was there thus any chance of rejecting the data he added as “non-significant”?

Is there any proof that his model is a useful representation of the actual atmosphere? None at all. But, hey, I may be wrong. I therefore challenge Lovejoy to use his model to predict future temperatures. If it’s any good, it will be able to skillfully do so. I’m willing to bet good money it can’t.

New York City’s St Patrick’s Day Parade Caves: Update

The three is for the Trinity.

The three is for the Trinity.

In the end they caved for the oldest of reasons. Money. And now, flush with cash, the world has yet another parade devoted to (anti-evolutionary) sexual desire.

As if we needed it.

Last year, anti-Catholic brewers Guinness and Heineken pulled funding for the parade in the name of “diversity” and “inclusion” and, of course, sodomy. This encouraged other sponsors to either do the same or threaten it this year.

Parade organizers, anxious for their fees, caved, though each undoubtedly wondered whether political leader Timothy Dolan, this year’s Grand Marshall, would forget that the purpose of the parade was “honor of the Patron Saint of Ireland and the Archdiocese of New York“.

They needn’t have fretted. The far-left New York Times reports Dolan saying that “[I] pray that the parade would continue to be a source of unity for all of us.”

At press time here, it was unknown whether Dolan offered that prayer to Saint Patrick.

Good thing for organizers they have Dolan and not some more recalcitrant leader like, say, this gentleman:

In 1993, then-Cardinal John O’Connor, facing gay protesters who staged a sit-in during the parade, vowed that he “could never even be perceived as compromising Catholic teaching” by entertaining their admission as an identifiable group in the event. “Neither respectability nor political correctness is worth one comma in the Apostles’ Creed,” O’Connor declared in his homily at a Mass for St. Patrick’s Day that year.

The parade has always allowed adulterers, murderers, thieves, pederasts, puppy haters, those who don’t call their mothers, and yes even those who are sexually “oriented” toward goats or toward those of the opposite sex. But none of those sinners—and each of us is—was allowed to carry a sign “celebrating” their personal favorite perversion.

Now they are.

Strike that. Now only the homosexuals are. Those sinners without advocacy groups will either have to get organized fast, or continue to disguise their noncomformities.

I ask you: is that fair?

Well, maybe it isn’t. But your mother was once legally allowed to ask you rhetorically, who said life was fair?

The dominoes have already began to tumble. The press is gleeful, naturally. Dolan, a masterful politician, murmurs nice-sounding nothings. And even walking volcano William Donohue, president of the Catholic League and former fighter-to-the-death, has been quieted. He said “there should be no controversy” at this year’s parade.

The committee that organizes the parade insists that it is “remaining loyal to church teachings”—except, of course, for those teachings which are expedient to disavow.

Which makes one wonder if these people really understand what they have done. Doubtful, very doubtful. Why?

Yours Truly lives in Manhattan and has been to this parade many times. The loudest cheers are usually for the garbage men who scoop up horseshit, though at times, active duty military units have had that honor, and on one notable occasion, even the cops (in 2002).

But is there anybody who will bet against me, for any amount, that this year it will be the unit which advertises it sexual hobbies? The press will be there in force. The other 300-some units, except for a bagpipe group which will flit across your screens to set the context, will be ignored. The parade will be all sodomy all the time.

We’ve all seen “pride” parades, and to call these lewd and lascivious would be a gross understatement. Yet the St Patrick’s parade probably won’t meet that fate, if only because snow is not rare on March 17th, and the route is cold and long. Still, I predict at least once incident of near undress, probably in the audience. Don’t worry about missing it. The media will be sure to spotlight it.

Since there will be at least two cameras per “LBGT” marcher, the high-school and pipe bands, police benevolent groups, and military veterans will become jealous. After this year, a few groups will elect to eschew the parade, half for the jealousy and half because of the abandonment of tradition.

The organizers this year are only allowing one “orientation” unit. This will not be seen to be enough. The 2016 parade will have at least three.

Finally, there will be some squirming about the name. Saint Patrick? Isn’t that rather religious? Why not be more inclusive and call it Paddy’s Day? An event where “all” (where “all” means politically active) are welcome?

Update Monsignor Pope: It’s time to cancel the St. Patrick’s Day Parade and the Al Smith Dinner. Looks like Msgr Pope took the post down. Curious, that.

Update Here’s why.

Update Rorate Caeli has the entire text of Msgr Pope’s original post. Worth a read. “We don’t need parades and dinner with people who scoff at our teachings, insist we compromise, use us for publicity, and make money off of us. W’’re being played for (and are?) fools.”

Exposure To Fracking Reduces Low-Birth-Weight Babies

Natural gas naturally leaking from ground in Taiwan, in the absence of all corporate and government supervision. Source.

Shouldn’t a peer-reviewed paper which purports to tie chemicals produced in the manufacture of natural gas (fracking etc.) to birth defects actually measure exposure (of fetus carriers, i.e. “mothers”) to those chemicals?

If you answered yes, you’ll never make it as an academic or government bureaucrat. Those folks know that successful careers are those which produce the most work for government.

As proof of this, take the peer-reviewed paper “Birth Outcomes and Maternal Residential Proximity to Natural Gas Development in Rural Colorado” in Environmental Health Perspectives by Lisa M. McKenzie and a slew of others, each of whom relies for their living on government.

Yet curiously, in a front page statement of “Competing Financial Interests”, those authors “declare they have no competing financial interests.”

It’s a side point, but all authors who rely on the increase and status of government should and must declare a conflict of interest just as authors who work for industry do. (More on this another day.)

Back to McKenzie. Here’s how Think Progress summarized her findings: Preliminary Studies Show Potential Health Risk For Babies Born Near Fracking Sites.

Preliminary, potential, risk. Who said science is political?

McKenzie was interested in the causes of congenital heart defects, neural tube defects, oral clefts, preterm birth, and term low birth weight. Besides naturally occurring genetic defects and defects caused by maternal folate deficiency, smoking drunkness and drug use, and other such things, it is suspected that exposure to benzene, toluene, polycyclic aromatic hydrocarbons, and petroleum based solvents might also cause congenital birth defects.

Here’s the winning phrase from the paper: “Many of these air pollutants are emitted during development and production of natural gas (referred to herein as NGD) and concerns have been raised that they may increase risk of adverse birth outcomes and other health effects” (and she cites herself as a source for this assertion).

Many of these pollutants are emitted? Okay, I’ll bite. Which? Which exact pollutants were the women in her study exposed to, and at what concentrations?

Answer: McKenzie doesn’t know. Nobody does. The epidemiologist fallacy has struck again.

The best she could do was to measure how far from a well location each mother lived at the time of birth. Where were those mothers before birth? Same addresses? Did they spend most of their pregnancy near the wells or away on vacation? What genetic characteristics did the people who lived near gas wells have that people who lived near the country club do not? How many women were drunks or druggies?

Answer: McKenzie doesn’t know. Nobody does.

McKenzie arbitrarily (to us readers, anyway) picked a 10-miles radius to label mothers “exposed”—to what, always remember, we don’t know. But doesn’t saying “exposed” sound scary? And being “exposed” to a mere gas well can’t hurt you unless you stub your toe on one.

And then came the wee p-values.

But not before manipulating the data in order to get it to work. Inexplicably, McKenzie divided living-near-gas-wells (what she called “exposure”) into terciles.

Unfortunately for headline hunters—I’m still amazed Think Progress missed this—wee p-values were found for decreased risk of low birth weight and preterm birth. Why did we not see in large print “Exposure To Fracking Reduces Low-Birth-Weight Babies”?

Or maybe the mothers who live away from the country club are younger and eat more heartily? Nah.

Another oopsie: oral clefts also appear to decline in frequency for some “exposed” women. So says a wee p-value. And no go for neural tube defects or congenital heart defects for the majority of “exposed” women. No go in the sense of no wee p-values for the “exposed”.

Only those in the highest arbitrary tercile evinced wee p-values (and small effects) for congenital and tube defects. Yet we have to ask which method McKenzie used to correct for the multiple statistical testing she did, i.e. all the hunting for signals. Well, you know the answer.

“Still, Briggs, what about those high terciles? Even if McKenzie manipulated the data, isn’t there something there?”

You’re forgetting that McKenzie never measured exposure to anything, but only distance from listed home residence to gas wells, and that some of her analysis showed benefits from this “exposure.” And since this isn’t real exposure, we have to adjust the analysis to account for the uncertainty of substituting addresses for exposure to unknown chemicals. Once that is done, the wee p-values would almost certainly swell past publishable size.

There is nothing but surmise, conjecture, wishful thinking in papers like this. Believing that fracking is bad for babies based on this paper is like convicting an accused murderer simply because he lived near the victim.

Dan Farber, Berkeley Lawyer, Confused Climate Clinger

According to the public figure's Facebook page, this is a self portrait.

According to the public figure’s Facebook page, this is a self portrait.

For the art of the sophist is the semblance of wisdom without the reality, and the sophist is one who makes money from an apparent but unreal wisdom. —Aristotle

Dan Farber calls himself a “public figure“, and I believe him.

Unfortunately, it’s not a distinguished category, and, given his performance (outlined below), the appellation invites unfortunate comparisons.

Rosie “9-11″ O’Donnell is a public figure, and so was Bozo the Clown (though the latter was beloved). And who could forget the People’s own scientist, comrade Trofim Lysenko?

But when I first read Farber’s “From germ theory to global warming, science denialism is beyond parody”, given the extreme violence he committed to calm reason and his mutilation of informed argument, the semblance which sprang to mind was public figure Jeffrey Dahmer.

Don’t think I’m picking on this heretofore unknown Dan Farber, God bless him. He is merely a symptom and not the disease. Delineating symptoms is an important part of understanding illness, however, so think of this article as a physician’s case report, all the while keeping in mind we’re dealing with a larger phenomenon than the mental corruption of one man.

Farber, like many, is a Climate Clinger. A man who, at least according to his public record, has no background in the science of fluid flow—would he, off the cuff, even know the atmosphere is a fluid? Did you?—yet who feels he knows enough to lecture his betters on (say) the modeling of radiative transfer using statistically derived inputs from satellites. How does instrument drift affect the input uncertainty?

Unburdened (it seems) with this knowledge, Farber apparently believes, and probably desires, the solution to global warming, but who (it’s a good bet) possess no real knowledge of the subject, beyond which he gleans from the media and other not-too-technical sources.

It’s surreal. It’s as if the bien pensant have been given their “talking points”, which they are able to parrot without having done the hard work of thinking, and who are so eager to please their masters that whoever is able to wound their enemies with the most vicious, facts-be-damned insult is to be awarded the highest position in that bright future which is to come.

Consider Farber’s feeble attempt to tie climate scientists who doubt the theory of apocalyptic global warming to those who deny the germ theory of illness.

If you’re inclined to doubt science, why not start with the germ theory of disease? After all, isn’t it implausible that illness, death, and even mass epidemics are caused by tiny invisible organisms that invade our bodies?

And what’s the evidence for that, really? Just the findings of scientists who can get big grants from NIH to study these so-called bacteria — not to mention studies financed by Big Pharm which makes a lot of money with supposed cures — and the views of doctors whose professional status and incomes are pumped up by their use of chemical antibiotics to treat diseases. And don’t forget about the massive government spending for sanitation and water treatment to eliminate “germs,” and the extensive regulation of the food industry, Big Government in action!

Sigh. This proves Farber has only read lightly, or has only retained little, of science history. That vapors, miasmas, and bad humors were the cause of disease was the consensus of the early nineteenth century. Why, 97% of scientists, and maybe even more, toed that line, and not only dared anybody to cross it, but they slew those who did.

Consider Ignaz Semmelweis who pleaded with his colleagues—with The Consensus—to at least listen to his arguments. Semmelweis’s reward? He was fired and hounded to an early grave.

The continued criticism and lash out finally broke him down. By 1865, he was suffering from depression, forgetfulness and other neural complaints and was eventually committed to an asylum. He only lasted there for two weeks and died on August 13, 1865 at the age of 47.

“When I look back upon the past, I can only dispel the sadness which falls upon me by gazing into that happy future when the infection will be banished…The conviction that such a time must inevitably sooner or later arrive will cheer my dying hour.”

Farber must have been possessed of a vague intuition that his intimation was ignorant, for he also said, “it turns out, there actually are germ denialists who accept that germs exist but don’t think they’re the real cause of disease. Rejection of the germ theory is found across the political spectrum…”.

That’s true, but misleading; because the stereotypical modern germ “denier” is a forty-four year-old first-time mother who aggressively pushes her stroller (affixed with faded “Obama-Biden 2012″ sticker) around Park Slope, Brooklyn, actively looking for reasons to be aggrieved. Curiously, this woman will also wholeheartedly “believe” in global warming.

So much for the disease. The cure? Since the malady feeds on (perceived or real) approbation, cut off its supply. With, say, articles like this.


Readers might have noticed the unusual number of qualifiers (“seems”, “probably”). Farber is a lawyer, and these folks when wounded have been known to abandon truth and to start barking about the law. It’s a good strategy, because it distracts their opponents while allowing them to avoid admitting they were wrong.

Philosophic Issues in Cosmology VIII: Foundational Propositions—Guest Post by Bob Kurland

George F.R.  Ellis

George F.R. Ellis

Bob Kurland is a retired, cranky, old physicist, and convert to Catholicism. He shows that there is no contradiction between what science tells us about the world and our Catholic faith.

Read Part VII. *Quotations, unless otherwise specified, are from Issues in the Philosophy of Cosmology, George F.R. Ellis.

One question in science is not “is this hypothetical model true” but “is this model better than the alternatives”…If we believe dogmatically in a particular view, then no amount of contradictory data will convince us otherwise… —John Skilling, “Foundations and Algorithms” in Bayesian Methods in Cosmology.

Scientific Criteria

Ellis gives as an important criteria for a scientific theory that it be empirically testable. My position may be even stronger than that of Ellis: if a theory cannot be confirmed by quantitative measurements then it is not in my view (and that of Fr. Stanley Jaki), science, but something else—mathematical metaphysics?

  • What can be confirmed by measurement is limited by the time, distance and physics horizons mentioned in the first post.
    Using electromagnetic radiation we cannot see further back in time than when radiation decoupled from matter, about 380,000 years after the origin.
  • We cannot see further in space than given by the distance horizon, the distance at which space will be expanding at faster than the speed of light.
  • We cannot duplicate the tremendous energies present in the initial, quantum stages of the beginning of the universe (these energies are orders of magnitude greater than even the huge energies that will be available in the SLAC Hadron supper collider), so we cannot test projected theories of particle creation.

What can be measured are inferred consequences of various theories: what the cosmic background radiation (CBR) shows about homogeneity, isotropy, fluctuations, the cosmological constant (lambda, representing expansion pressure), etc. Recent examples are the report of Gurzadyan and Penrose of rings in the CBR representing cataclysmic events pre-Big Bang and B-mode measurements of the CBR from which are inferred gravitational waves in the early universe and thus inflation. One may disagree with the aspects of the theory, but the tie-in with measured data is commendable.


Ellis gives a series of theses for his position. The theses in Issue F, “The explicit philosophic basis”, are presented in detail. As a preliminary and review, here are Ellis’s theses pertinent to the science of cosmology.

  • THESIS A1: The universe itself cannot be subjected to physical experimentation. We cannot re-run the universe with the same or altered conditions to see what would happen if they were different , so we cannot carry out scientific experiments on the universe itself.
  • THESIS A2: The universe cannot be observationally compared with other universes. We cannot compare the universe with any similar object, nor can we test our hypotheses about it by observations determining statistical properties of a known class of physically existing universes.
  • THESIS B3: Establishing a Robertson-Walker geometry for the universe relies on plausible philosophic assumptions. The deduction of spatial homogeneity follows not directly from astronomical data but because we add to the observations a philosophical principle that is plausible but untestable.

In Thesis B3, Ellis refers to the notion that the universe is isotropic and homogeneous (on a large scale). From our vantage point, we can see that the CBR (cosmic background radiation) yields this result; but to show that the inference is valid for the universe as a whole, we would need to make the same observation from at least two other (far removed) vantage points. However, if the Copernican Principle is invoked that we do not occupy a special place in the universe (this is the philosophic principle Ellis refers to in Thesis B3), then what see is equivalent to what would be seen from other positions, and the homogeneity and isotropy is demonstrated.

  • THESIS B6: Observational horizons limit our ability to observationally determine the very large scale geometry of the universe. We can only see back to the time of decoupling of matter and radiation and so have no direct information about earlier times; and unless we live in a ‘small universe’, most of the matter in the universe is hidden behind the visual horizon. Conjectures as to its geometry on larger scales cannot be observationally tested. The situation is completely different in the small universe case: then we can see everything there is in the universe, including our own galaxy at earlier times! (emphasis and exclamation point added)
  • THESIS C1: The Physics Horizon limits our knowledge of physics relevant to the very early universe. We cannot experimentally test much of the physics that is important in the very early universe because we cannot attain the required energies in accelerators on Earth. We have to extrapolate from known physics to the unknown and then test the implications; to do this, we assume some specific features of known lower energy physics are the true key to how things are at higher energies. We cannot experimentally test if we have got it right.
  • THESIS C2: The unknown nature of the inflation means inflationary universe proposals are incomplete. The promise of inflationary theory in terms of relating cosmology to particle physics has not been realized. This will only be the case when the nature of the inflaton (the particle representing the scalar force causing inflation)has been pinned down to a specific field that experiment confirms or particle physics requires to exist.
  • THESIS D2: Testable physics cannot explain the initial state and hence specific nature of the universe. (emphasis added)

Ellis expands on Thesis D2 as follows:

A choice between different contingent possibilities has somehow occurred; the fundamental issue is what underlies this choice. Why does the universe have one specific form rather than another, when other forms consistent with physical laws seem perfectly possible? The reason underlying the choice between different contingent possibilities for the universe (why one occurred rather than another) cannot be explained scientifically. It is an issue to be examined through philosophy or metaphysics. (emphasis added).

This last proposition is, I believe, the most important of those Ellis sets forth.

  • THESIS E1: Physical laws may depend on the nature of the universe.

Philosophic Criteria

  • THESIS F1: Philosophic choices necessarily underlie cosmological theory.Unavoidable metaphysical issues inevitably arise, in both observational and physical cosmology. Philosophical choices are needed in order to shape the theory.
  • THESIS F2: Criteria of satisfactoriness for theories cannot be scientifically chosen or validated. Criteria of satisfactoriness are necessary for choosing good cosmological theories; these criteria have to be chosen on the basis of philosophical considerations. They should include criteria for satisfactory structure of the theory, intrinsic explanatory power, and observational and experimental support. These criteria are listed below:
  1. Satisfactory structure: a) internal consistency, b) simplicity (Ockham’s razor), and c) aesthetic appeal (‘beauty’ or ‘elegance’)
  2. Intrinsic explanatory power: a) logical tightness, b) scope of the theory—the ability to unify otherwise separate phenomena, and c) probability of the theory or model with respect to some well-defined measure.
  3. Extrinsic explanatory power, or relatedness: a) connectedness to the rest of science, b) extendability providing a basis for further development;
  4. Observational and experimental support, in terms of a) testability: the ability to make quantitative as well as qualitative predictions that can be tested; and b) confirmation: the extent to which the theory is supported by such tests as have been made. (emphasis added)

The last criterion in my view (and that of many other scientists and philosophers of science) is critical. If a theory cannot in principle be confirmed quantitatively it is not science, but belongs to other disciplines.

  • THESIS F3: Conflicts will inevitably arise in applying criteria for satisfactory cosmological theories. Philosophical criteria for satisfactory cosmological theories will in general come into conflict with each other, so that one will have to choose between them to some degree; this choice will shape the resulting theory.

Ellis elaborates on this last thesis:

The thrust of much recent development has been away from observational tests towards strongly theoretical based proposals, indeed sometimes almost discounting observational tests. At present this is being corrected by a healthy move to detailed observational analysis of the proposed theories, marking a maturity of the subject. (emphasis added)

  • THESIS F4: The physical reason for believing in inflation is its explanatory power as regards structure growth in the universe. … This theory has been vindicated spectacularly through observations of the CBR and matter power spectra. It is this explanatory power that makes it so acceptable to physicists, even though the underlying physics is neither well-defined nor tested, and its major large-scale observational predictions are untestable. (emphasis added).

Expanding on Thesis F4, Ellis adds:

Inflation provides a causal model that brings a wider range of phenomena into what can be explained by cosmology (Criterion 2b), rather than just assuming the initial data had a specific restricted form. Explaining flatness (omega0 approximately 1, as predicted by inflation) and homogeneity reinforces the case, even though these are philosophical rather than physical problems (they [the initial restricted conditions] do not contradict any physical law; things could just have been that way). However claims on the basis of this model as to what happens very far outside the visual horizon (as in the chaotic inflationary theory) results from prioritizing theory over the possibility of observational and experimental testing. It will never be possible to prove these claims are correct. (emphasis added)

Ellis asks, “how much should we try to explain” with cosmology? What should the scope of cosmology include?

  • THESIS F5:Cosmological theory can have a wide or narrow scope of enquiry. The scope we envisage for our cosmological theory shapes the questions we seek to answer. The cosmological philosophical base becomes more or less dominant in shaping our theory according to the degree that we pursue a theory with more or less ambitious explanatory aims in terms of all of physics, geometry and underlying fundamental causation.

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