Archive for the ‘Philosophy’ Category

Arvin Ash is an engineer with a YouTube channel. He recently posted a video titled “Is God in Physics? Fine Tuning Scrutinized“. It gets almost everything wrong: history, philosophy, science, and fine-tuning. All quotes from the video, unless noted otherwise.

A. Motion in the heavens

Until 350 years ago, there was a distinct demarcation between what people observed on Earth and what people saw up in the sky. There did not seem to be any connection. Things that happened on Earth could at least be seen and explained at least in terms of cause and effect. The Heavens seemed to be an utter mystery. The motions of the planets, though predictable, did not appear to follow the same patterns as objects here on Earth. To many this was the sign of the hand of a Creator. It must be God that ruled over the universe, controlling the movement of these heavenly bodies, and to gaze at the stars was to bear witness to the majesty of God’s design. [0:15]

We’re off to a terrible start. The Heavens were not an “utter mystery” to the ancients – Aristotle’s physics included the heavens. The planets and stars behaved differently to Earthly elements (earth, water, air, fire) because they were made out of different stuff. (more…)


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Before I get onto Carroll’s other replies to the fine-tuning argument, I need to discuss a feature of naturalism that will be relevant to what follows.

I take naturalism to be the claim that physical stuff is the only stuff. That is, the only things that exist concretely are physical things. (I say “concretely” in order to avoid the question of whether abstract things like numbers exist. Frankly, I don’t know.)

On naturalism, the ultimate laws of nature are the ultimate brute facts of reality. I’ve discussed this previously (here and here): the study of physics at any particular time can be summarised by three statements:

  1. A list of the fundamental constituents of physical reality and their properties.
  2. A set of mathematical equations describing how these entities change, interact and rearrange.
  3. A statement about how the universe began (or some other boundary condition, if the universe has no beginning point).

In short, what is there, what does it do, and in what state did it start?

Naturalism is the claim that there is some set of statements of this kind which forms the ultimate brute fact foundation of all concrete reality. There is some scientific theory of the physical contents of the universe, and once we’ve discovered that, we’re done. All deeper questions – such as where that stuff came from, why it is that type of stuff, why it obeys laws, why those laws, or why there is anything at all – are not answerable in terms of the ultimate laws of nature, and so are simply unanswerable. They are not just in need of more research; there are literally no true facts which shed any light whatsoever on these questions. There is no logical contradiction in asserting that the universe could have obeyed a different set of laws, but nevertheless there is no reason why our laws are the ones attached to reality and the others remain mere possibilities.

(Note: if there is a multiverse, then the laws that govern our cosmic neighbourhood are not the ultimate laws of nature. The ultimate laws would govern the multiverse, too.)

Non-informative Probabilities

In probability theory, we’ve seen hypotheses like naturalism before. They are known as “non-informative”.

In Bayesian probability theory, probabilities quantify facts about certain states of knowledge. The quantity p(A|B) represents the plausibility of the statement A, given only the information in the state of knowledge B. Probability aims to be an extension of deductive logic, such that:

“if A then B”, A -> B, and p(B|A) = 1

are the same statement. Similarly,

“if A then not B”, A -> ~B and p(B|A) = 0

are the same statement.

Between these extremes of logical implication, probability provides degrees of plausibility.

It is sometimes the case that the proposition of interest A is very well informed by B. For example, what is the probability that it will rain in the next 10 minutes, given that I am outside and can see blue skies in all directions? On other occasions, we are ignorant of some relevant information. For example, what is the probability that it will rain in the next 10 minutes, given that I’ve just woken up and can’t open the shutters in this room? Because probability describes states of knowledge, it is not necessarily derailed by a lack of information. Ignorance is just another state of knowledge, to be quantified by probabilities.

In Chapter 9 of his textbook “Probability Theory” (highly recommended), Edwin Jaynes considers a reasoning robot that is “poorly informed” about the experiment that it has been asked to analyse. The robot has been informed only that there are N possibilities for the outcome of the experiment. The poorly informed robot, with no other information to go on, should assign an equal probability to each outcome, as any other assignment would show unjustified favouritism to an arbitrarily labeled outcome. (See Jaynes Chapter 2 for a discussion of the principle of indifference.)

When no information is given about any particular outcome, all that is left is to quantify some measure of the size of the set of possible outcomes. This is not to assume some randomising selection mechanism. This is not a frequency, nor the objective chance associated with some experiment. It is simply a mathematical translation of the statement: “I don’t know which of these N outcomes will occur”. We are simply reporting our ignorance.

At the same time, the poorly informed robot can say more than just “I don’t know”, since it does know the number of possible outcomes. A poorly informed robot faced with 7 possibilities is in a different state of knowledge to one faced with 10,000 possibilities.

A particularly thorny case is characterising ignorance over a continuous parameter, since then there are an infinite number of possibilities. When a probability distribution for a certain parameter is not informed by data but only “prior” information, it is called a “non-informative prior”. Researchers continue the search for appropriate non-informative priors for various situations; the interested reader is referred to the “Catalogue of Non-informative Priors”. (more…)

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More on the upcoming Carroll vs. Craig dialogue (previously, one, two, three). I have some leftover business from my previous post on the contingency argument for the existence of God. It concerns the question why is there something something rather than nothing?, a question I’ve discussed on a few previous occasions.

The Question

The question “why is there something something rather than nothing?” is not an argument, obviously. It’s a question. It’s relationship to the cosmological argument for the existence for God is as an entree, a taster. It’s supposed to get you thinking about existence.

Imagine two parties. At one is everything that actually exists (or has existed) – the “actual” party. At the other, everything that could exist – the “possible” party. Horses are at both parties, unicorns only the possible party. Why? Because of something at the actual party, in this case the evolutionary ancestors of the horse. When something moves from possible to actual, it’s because of an invitation from the actual party. Those in the possible party can’t crash the actual party. They don’t exist, and so don’t have any causal powers, so can’t make anything actually happen.

So this actual party – did everyone get their invitation off someone else? Is there an infinite regress of inviters? It can’t form a loop – I invite you and you invite me – because that’s just crashing the party. Could there be a party where everyone must be invited by someone who’s already there? Why is anyone at the party? Why does anything exist?

Not the Question

Aside: The question is not: “something came from nothing. How could that happen?”, to which the answer is supposedly: because God can make something out of nothing. That confuses the contingency argument with the Kalam argument. The question is “Why is there something rather than nothing?”. The answer is: God is a necessary being, so it is not possible for there to be nothing. God must exist.

Nothing, Naturally

Carroll discusses the question “why is there something rather than nothing?” in this blog post. Amongst other things, he discusses the claim that “nothingness is uniquely natural”, so that we need some special reason why something exists. He argues that we have no basis for such a conclusion, as our intuitions for naturalness and simplicity are based on our experience in this world, and so don’t automatically apply to the universe itself.

However, most versions of the cosmological argument don’t explicitly appeal to the naturalness of nothing. Carroll, following Grunbaum, discusses Swinburne. In Grunbaum’s paper “Why is There a World AT ALL, Rather Than Just Nothing?”, he quotes Swinburne: “It remains to me, as to so many who have thought about the matter, a source of extreme puzzlement that there should exist anything at all” (pg. 336). I think, however, they’ve missed the point of what Swinburne is saying. (I say this with some trepidation. Grunbaum is a professional philosopher, and something of a legend. Fools rush in …) (more…)

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As I explained in my last posts (one, two), I’m expecting good things from the upcoming dialogue between Sean Carroll and William Lane Craig. Here, I’ll look at a species of the cosmological argument for the existence of God known as the contingency argument.

Before all that: Sean has linked to my previous post about this debate. Just to be clear, I don’t think Sean needs much advice. I’m really using these posts as an excuse to discuss Carroll’s ideas. He knows the arguments, knows the cosmology, has a clear idea about what naturalism is and how to defend it, and is an excellent public speaker. Carroll’s arguments are interesting and relevant, and Craig’s response won’t be anything as basic as “here’s a Grammar 101 lesson on using terms of negation and indefinite pronouns.”

Long post ahead. The short story: Carroll needs to make clear his objection to the Craig’s version of the principle of sufficient reason. In particular, why think that the universe is an exception (perhaps the only exception) to the general trend that things exist for a reason?

Craig’s Version of the Argument

The cosmological argument for the existence of God has been defended through the ages by a who’s who of thinkers: Plato, Aristotle, Al-Kindi, Ibn Sina, Al-Ghazali, Maimonides, Aquinas, Scotus, Spinoza, Leibnitz, … Of course, it has also been critiqued, most famously by Hume and Kant. The debate continues. Craig’s version of the contingency argument goes like this.

  1. Everything that exists has an explanation of its existence (either in the necessity of its own nature or in an external cause).
  2. If the universe has an explanation of its existence, that explanation is God.
  3. The universe exists.

It follows from these premises that God exists (homework). Note that this argument has nothing to do with whether the universe has a beginning.

Some atheists (Lawrence Krauss in particular) object to the second premise, thinking that God is just crowbarred in, an ad hoc assumption. But premise 2 has its own argument:

4. Since the universe is the totality of space, time, matter and energy (i.e. that’s the sense of universe being used here), the cause of the universe must be spaceless, timeless, and immaterial.
5. The most plausible immaterial kind of thing that could cause a universe is a mind.
6. A spaceless, timeless, and immaterial mind that causes the universe deserves to be called God.

Premise 5, in turn, has its own argument based on the causal effeteness of abstract entities. If you want to go after premise 2, you need to deal with this argument. Krauss didn’t.

Getting slightly ahead of myself, Carroll seems to object to Premise 1. This premise is a version of the infamous Principle of Sufficient Reason (PSR). It is a mild version, applying only to things, not to all (contingent) truths. Craig argues for premise 1, or at least that the universe is not an exception to premise 1, as follows.

  1. It would be arbitrary for the atheist to claim that the universe is the exception to the rule. Merely increasing the size of the object to be explained, even until it becomes the universe itself, does nothing to remove the need for some explanation of its existence.

Alexander Pruss has advanced arguments for a version of the PSR along these lines. (I’m paraphrasing, dangerously).

8. If the universe could exist without explanation, then it would be inexplicable why just anything couldn’t exist without explanation. In other words, why is only the universe an exception to premise 1?
9. Universal principles are simpler than principles that apply to an arbitrary subset. The simplest explanation of fact that contingent things typically have explanations is that all contingent things have explanations.

Carroll’s Case

Let’s consider with what Carroll’s response might be, as gleaned from this reply to an op-ed piece by Paul Davies.

“[A]t first glance, it seems plausible that there could be [an] answer to the question of why the laws of physics take the form they do. But there isn’t. At least, there isn’t any as far as we know, and there’s certainly no reason why there must be. The more mundane “why” questions make sense because they refer to objects and processes that are embedded in larger systems of cause and effect. … The universe (in the sense of “the entire natural world,” not only the physical region observable to us) isn’t like that. It’s not embedded in a bigger structure; it’s all there is. We are lulled into asking “why” questions about the universe by sloppily extending the way we think about local phenomena to the whole shebang. What kind of answers could we possibly be expecting? … [The correct possibility seems to be] that’s just how things are. There is a chain of explanations concerning things that happen in the universe, which ultimately reaches to the fundamental laws of nature and stops. This is a simple hypothesis that fits all the data; until it stops being consistent with what we know about the universe, the burden of proof is on any alternative idea for why the laws take the form they do.”

Let’s break it down. Lurking in the background of this entire discussion is this question: what makes an explanation an ultimate explanation? What is it about this explanation that makes another iteration of “and why?” out-of-bounds? Carroll’s argument seems to be:

10. Chains of explanations have to end somewhere.
11. Once we arrive at a simple explanation that fits all the data, there is nothing to be gained by going any further. Such an explanation should be considered an ultimate “stopping-point” explanation.
12. The fundamental laws of nature are just such an explanation for the physical universe.
13. Thus, we should consider the fundamental laws of nature to be the ultimate explanation of the universe.

Carroll’s formula of “simplicity + fits the data” needs a closer look. (more…)

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As I explained in my last post, I’m expecting good things from the upcoming dialogue between Sean Carroll and William Lane Craig. Before discussing the topic, a few comments about debating.

An awful lot of rubbish has been written about counteracting Craig’s diabolical debating; it’s actually pretty simple. When you speak, make a clear argument for a relevant conclusion. After he speaks, target specific premises of his arguments and explain why you think they are unlikely to be true. That’s it. It sounds simple, and it’s been done very effectively, but so many of Craig’s opponents can’t manage it.

Critics have said that Craig unfairly dictates the flow of the debate, keeping a stranglehold on the topic of his choosing. This doesn’t happen when his opponent keeps him busy. Austin Dacey and Keith Parsons are great examples. Craig won’t ignore your case if you make one, and it’s relevant. Give him something to respond to.

If you fail to make a case, Craig will have read your writings and be prepared to both make your own case for you and critique it. He did this to great effect against Rosenberg. If you fail to address his arguments, he will point this out and repeat them. He is justified in doing so because one often hears the refrain that “I’m an atheist because there’s no evidence for God”. To maintain that there is no evidence, one must be able to explain why the supposed evidence isn’t really evidence at all. As an analogy, one cannot reasonably claim that “there is no evidence that human beings walked on the moon” and not attempt to explain the Apollo 11 photographs and videos.

There is no excuse for debating Craig underprepared. You can listen to a debate from the early 1990’s and get most of his arguments. That said, you are better off reading an article rather than responding to a 20 minute summary. It’s best not to raise objections that he has already addressed in print, or even better, raise them in a way that also addresses his response.

Always go for the argument, never the man. If you’ve shown that Craig is mistaken, then it doesn’t much matter how he convinced himself of such falsehoods. Amateur anthropology/psychology/neuroscience – e.g. any sentence beginning with “human beings have a very strong cognitive bias to believe …” – is a waste of time. Just burn down his arguments; don’t toast marshmallows on the embers. Resist Bulverism!

Remember: critiquing is hard. That someone is wrong doesn’t make it easier. Step 1: understand. Step 2: critique. Here are a few resources. Feel free to add more in the comments.

Kalam Cosmological Argument

Contingency (Leibnizian) Argument

  • I think the most comprehensive presentation of Craig’s version of the argument is in his book “Reasonable Faith”. A shorter (and free) introduction is here.

  • Some of the “Questions of the week” shed more light on the philosophical issues that arise: 132, 190, 248, 329.

  • I recommend Alexander Pruss’ article on the Leibnizian argument in the Blackwell Companion to Natural Theology. Craig calls it “a must”, but be aware that it differs from Craig’s version in both content and style. In particular, Pruss defends a more comprehensive version of the principle of sufficient reason.

Fine-Tuning Argument

  • Again, the book “Reasonable Faith” is the best resource. A slightly older presentation is here.

  • Questions of the weeks that address the argument: 49, 63, 161, 313. In particular, Craig’s response to the multiverse, include the Boltzmann Brain problem: 14, 285.

  • For the scientific details of the argument, Craig relies a lot on the work of Robin Collins. Collins’ best presentation of fine-tuning cases is in this book. He presents the argument itself in the Blackwell Companion to Natural Theology. He has an interesting discussion of the implications of the Boltzmann brain problem in this article.

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On February 21-22 (2014), Sean Carroll and William Lane Craig will debate at the Greer-Heard Forum, at the New Orleans Baptist Theological Seminary. The topic is “God and Cosmology: The Existence of God in Light of Contemporary Cosmology”. For a number of reasons, I have high hopes for this one. Here’s why.

I (mostly) like the format

We start with a dialogue between the two parties, for 1.5 hours. As a spectator, I prefer the debate format. While a dialogue sounds like a friendly chat rather than a confrontation, in practice it unfairly unfavors the rude and the loud. We are at the mercy of the disciplinary skill of the moderator. However, this one shouldn’t be too bad. Craig will let his opponent talk, and I get the same impression from Carroll.

Given the list of things I’d like them to discuss, as I’ll discuss in future posts, I’m hoping that each party gets an opening statement of at least 20 minutes. They both have a lot to say about this topic, and need the time to present their case thoroughly.

The next day we’re back with 4 speakers, each with an hour that includes responses from Carroll and Craig. That’s a very interesting arrangement and I’m keen to see how it works in practice. The day rounds out with concluding comments from the two debaters.

Good choice of debaters

I’ve listened to a number of William Lane Craig’s debates and the best ones are usually against other philosophers, for this reason. The topic is God, or at least something closely related to the almighty. In any argument for or against the existence of God, at least one of the premises must be metaphysical. So against, say, a scientist, Craig can absorb a lot of the scientific expertise of his opponent and focus on the (often unstated) philosophical assumptions behind their remarks. The debate moves to matters philosophical, which gives Craig the home advantage. Some of Craig’s opponents know less than nothing about philosophy; what they think they know about philosophy is wrong. On the other hand, Craig knows enough of the science that is relevant to his arguments to be able to defend the scientific premises against a philosopher.

Carroll has an undergraduate philosophy minor and as a grad student in astrophysics at Harvard, sat in on courses with John Rawls and Robert Nozick. His blog posts and articles show a familiarity with and respect for philosophical issues. Carroll is close to the ideal opponent for this debate, as he should be able to hold his own on matters philosophical, whilst holding a substantial advantage on matters cosmological.

Good Choice of Respondents

I’m guessing that Craig will defend three of his usual five arguments – the Kalam cosmological argument from the beginning of the universe, the contingency argument, and the design argument from the fine-tuning of the universe for intelligent life. The contingency argument doesn’t rely on any particular scientific theories, so Craig doesn’t need any particular backup on that front. For the Kalam cosmological argument, his scientific case for the premise “the universe has a beginning” has been provided in recent times by James Sinclair. In particular, Craig’s most sophisticated defence of the argument in recent times is in the The Blackwell Companion to Natural Theology, which was co-written with Sinclair. Sinclair is a Warfare Analyst with a masters in cosmology, so his credentials are slightly unorthodox.

Also writing in the The Blackwell Companion to Natural Theology is Robin Collins, a philosopher with a background in physics. He has specialised in the argument from the fine-tuning of the universe for intelligent life. So that gives Craig his backup for his third argument.

Carroll has two philosophers in tow. Alex Rosenberg is a philosopher at Duke University who Craig has debated before, and whose book “The Atheist’s Guide to Reality” was praised by both sides of the debate as seeing rather clearly the consequences of atheism. Tim Maudlin is a philosopher of science at New York University. His book “Philosophy of Physics: Space and Time” is marvellous. He also seems to have taken an interest in the fine-tuning of the universe for intelligent life. (I have a few reservations about his opinions on that topic.)

That’s an interesting line up. I’d gladly hear any of them speak on the topic at hand; all four of them in a row with responses from Carroll and Craig is very promising.

My advice

I think this debate could be uniquely insightful on this important topic. Craig has said an awful lot about cosmology in recent years, and no one has really pressed him on the details. They’ve mostly (though not unreasonably) appealed to cosmological authorities. (For the love of Pete, nobody read out an email from Alex Vilenkin. More on that soon.) Carroll has said a lot about the implications of cosmology for theism, and there are some philosophical niceties to be examined there as well. Stay tuned for parts two, three, and four.

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I recently read philosopher of science Tim Maudlin’s book Philosophy of Physics: Space and Time and thought it was marvellous, so I was expecting good things when I came to read Maudlin’s article for Aeon Magazine titled “The calibrated cosmos: Is our universe fine-tuned for the existence of life – or does it just look that way from where we’re sitting?“. I’ve got a few comments. Indented quotes below are from Maudlin’s article unless otherwise noted.

In a weekend?

Theories now suggest that the most general structural elements of the universe — the stars and planets, and the galaxies that contain them — are the products of finely calibrated laws and conditions that seem too good to be true. … The details of these sorts of calculations should be taken with a grain of salt. No one could sit down and rigorously work out an entirely new physics in a weekend.

Two few quick things. “Theories” has a ring of “some tentative, fringe ideas” to the lay reader, I suspect. The theories on which one bases fine-tuning calculations are precisely the reigning theories of modern physics. These are not “entirely new physics” but the same equations (general relativity, the standard model of particle physics, stellar structure equations etc.) that have time and again predicted the results of observations, now applied to different scenarios. I think Maudlin has underestimated both the power of order of magnitude calculations in physics,  and the effort that theoretical physicists have put into fine-tuning calculations. For example, Epelbaum and his collaborators, having developed the theory and tools to use supercomputer lattice simulations to investigate the structure of the C12 nucleus, write a few papers (2011, 2012) to describe their methods and show how their cutting-edge model successfully reproduces observations. They then use the same methods to investigate fine-tuning (2013). My review article cites upwards of a hundred papers like this. This is not a back-of-the-envelope operation, not starting from scratch, not entirely new physics, not a weekend hobby. This is theoretical physics.

Telling your likelihood from your posterior

It can be unsettling to contemplate the unlikely nature of your own existence … Even if your parents made a deliberate decision to have a child, the odds of your particular sperm finding your particular egg are one in several billion. … after just two generations, we are up to one chance in 10^27. Carrying on in this way, your chance of existing, given the general state of the universe even a few centuries ago, was almost infinitesimally small. You and I and every other human being are the products of chance, and came into existence against very long odds.

The slogan I want to invoke here is “don’t treat a likelihood as if it were a posterior”. That’s a bit to jargon-y. The likelihood is the probability of what we know, assuming that some theory is true. The posterior is the reverse – the probability of the theory, given what we know. It is the posterior that we really want, since it reflects our situation: the theory is uncertain, the data is known. The likelihood can help us calculate the posterior (using Bayes theorem), but in and of itself, a small likelihood doesn’t mean anything. The calculation Maudlin alludes to above is a likelihood: what is the probability that I would exist, given that the events that lead to my existence came about by chance? The reason that this small likelihood doesn’t imply that the posterior – the probability of my existence by chance, given my existence – is small is that the theory has no comparable rivals. Brendon has explained this point elsewhere. (more…)

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Having had my appetite for the Middle Ages whetted by Edward Grant’s excellent book A History of Natural Philosophy: From the Ancient World to the Nineteenth Century, I recently read Edward Feser’s Aquinas (A Beginner’s Guide). And, on the back of that, his book The Last Superstition. If I ever work out what a formal cause is, I might post a review.

In the meantime, I’ve quite enjoyed some of his blog posts about the philosophical claims of Lawrence Krauss. This is something I’ve blogged about a few times. His most recent post on Krauss contains this marvellous passage.

Krauss asserts:

“[N]othing is a physical concept because it’s the absence of something, and something is a physical concept.”

The trouble with this, of course, is that “something” is not a physical concept. “Something” is what Scholastic philosophers call a transcendental, a notion that applies to every kind of being whatsoever, whether physical or non-physical — to tables and chairs, rocks and trees, animals and people, substances and accidents, numbers, universals, and other abstract objects, souls, angels, and God. Of course, Krauss doesn’t believe in some of these things, but that’s not to the point. Whether or not numbers, universals, souls, angels or God actually exist, none of them would be physical if they existed. But each would still be a “something” if it existed. So the concept of “something” is broader than the concept “physical,” and would remain so even if it turned out that the only things that actually exist are physical.

No atheist philosopher would disagree with me about that much, because it’s really just an obvious conceptual point. But since Krauss and his fans have an extremely tenuous grasp of philosophy — or, indeed, of the obvious — I suppose it is worth adding that even if it were a matter of controversy whether “something” is a physical concept, Krauss’s “argument” here would simply have begged the question against one side of that controversy, rather than refuted it. For obviously, Krauss’s critics would not agree that “something is a physical concept.” Hence, confidently to assert this as a premise intended to convince someone who doesn’t already agree with him is just to commit a textbook fallacy of circular reasoning.

The wood floor guy analogy is pretty awesome, so be sure to have a read.

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The ABC’s opinion pages has posted my introduction to the debate between Lawrence Krauss and William Lane Craig, happening this evening at the Sydney Town Hall. The debate topic is “Why is there something rather than nothing?”. Can science answer the question? Can God? Can anyone? Read on.


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(In which I make fairly uncontroversial points about evidence using controversial examples, thus providing my own red herring.)

There is a logical fallacy known as appealing to authority, which goes like this.

1. X believes Y

2. X is very clever / a well known expert / a professor / a reliable person …

3. Thus, Y is true

This is a fallacy because people can be wrong, even smart people.

However, we all believe things because someone told us so. We would make impossibly slow progress in life if we had to verify every belief for ourselves. There are people we usually trust – not blindly but because they’ve proven trustworthy. 

Modern science has a rather strained relationship with authority. On the one hand, much of science’s early progress came from following the maxim: “don’t believe everything Aristotle said”. If you want to know what the natural world is like, go ask the natural world. Go into the lab, go get a telescope, go find out for yourself. Experiments shouldn’t just be repeatable. They should be repeated.

On the other hand, science has made so much progress, collected so much data, published so many papers that no one person can have checked it all out for themselves. The astronomy preprint archive posts about 100 new astronomy papers per day. We are reliant on the honesty and competence of other scientists who provide us with measurements, constants, equations, simulations. We can check some of it but not all.

The layman is in an even worse position, as they may not have the training, time and skills to verify the conclusions of science even if they wanted to. Should Jo(e) Public believe that the universe is expanding because scientists say so? Or should they build their own telescope, invent the spectrometer, locate and observe distant galaxies, measure atomic emission spectra, calculate the recession velocities of the galaxies, observe Cepheid variable stars, discover their period-magnitude relation, use this relation to measure the distance to galaxies, note the linear dependence of velocity on distance, discover general relativity, solve for an expanding spacetime, derive the linear dependence of velocity on distance, and then (and only then) conclude that the universe is expanding?

The truth, of course, is somewhere in the middle: Jo(e) public can understand how scientists have reached the conclusion that the universe is expanding, so that this central pillar of the Big Bang theory is not pure assertion. They can follow our path on a map, as it were, even if they do not tread every step again themselves. Science ultimately appeals to observations of the natural world, even if they are usually someone else’s observations.

So when should we believe an authority? When does quoting an authority commit the aforementioned fallacy? The key is to be specific about what is being claimed.

Authority as evidence

We mustn’t confuse knowledge with certainty. We need to reason using probabilities. Bayes theorem teaches us how to update our probabilities when new, relevant information comes to light. Learning that a particular expert believes something is new, relevant information. It may not be decisive, but shouldn’t be ignored. 

1′. X believes Y

2′. X is in a position to assess the evidence for and against Y. X is informed, competent, experienced, has a reputation for honesty, has no conflict of interest etc.

3′. Thus, the probability of Y being true has increased.

A belief is justified or warranted if it was formed using reliable methods, which can be counted on to produce true beliefs most of the time. Recognising those methods in another person adds weight to their opinion.

Authority as establishing the burden of proof

I really shouldn’t choose such a hot-button topic to make a point like this, but it’s such a good example that I can’t resist. Take climate change. The majority of the climate science community has concluded that the evidence supports the hypothesis that human activity has and will lead to substantial, detrimental changes to our planet’s climate. 

Does that prove that climate change is real? No. Proving is something that mathematicians do. It does, however, set the standard for those who believe that climate change is not real. The scientific consensus is prima facie evidence of the truth of climate change. Jo(e) Public is justified, in the absence of the time and skills to investigate for themselves, in believing that climate change is more likely to be true than false. Those who wish to believe that climate change is probably not real have the burden of showing that the scientists are wrong.

This is an application of my last point – authority as evidence. The consensus of an expert, informed community tips the scales in favour of climate change. The pronouncements of scientists are not infallible, but should not be rejected without good scientific reasons. Political conservativism, conspiracy theories and a desire to be viewed as an “iconoclast” are not good reasons.

Authority and Relevance

A key idea in the previous section was relevance. When an climate scientist reaches a conclusion about the state of the Earth’s climate, he is commenting on exactly the thing that s/he studies. There is a danger of experts being viewed as generically clever and thus authorities in any field they care to address. As usual, xkcd summarises the point beautifully.


Another controversial example. I once saw someone on TV (possibly a news vox pop), when asked about life after death, cite as conclusive evidence the fact that Stephen Hawking doesn’t believe that there is life after death. Now, I have every respect for the prodigious talents of Professor Hawking, a scientist above whom the superlative “greatest” justifiably hovers. But none of the things that Hawking has done to gain his reputation have anything to do with life after death. He is an expert on quantum gravity, black holes, general relativity, and the cosmology of the very early universe.

Is there any evidence for life after death? Near death experiences, religious revelation, philosophical (metaphysical) arguments for the immateriality of the soul, and widespread belief in life after death around the world and throughout history are the factors usually cited. So the relevant areas of expertise are medicine, especially neuroscience, as well as a familiarity with the claims of witnesses, the psychology of human beings (e.g. fear of death), philosophy, comparative religion, etc. Life after death is usually taken to be incompatible with philosophical materialism, so philosophical arguments for materialism are also relevant. Prof. Hawking is not an expert in any of these areas. There are, I assume, plenty of doctors, neuroscientists, psychologists and philosophers with the relevant expertise who discount near death experiences and the afterlife. If you want to cite an authority, cite them. Hawking’s opinion in this area is worthy of consideration, of course, but not authoritative.

Beware of 8 out of 10 Authorities

The previous point applies a fortiori to surveys of experts. For example, the fact that a larger-than-average percentage of scientists do not believe in God would seem to explain itself. But there is a possible selection effect. It’s the same selection effect that one may suspect is behind the fact that, while (roughly) 80% of philosophers are atheists, this drops to just 20% of those philosophers who specialise in philosophy of religion.

It’s the same old correlation vs. causation story. Did a random sample enter both fields, and thereafter have their views moulded by their respective subject matter? Or did a prior belief in God lead some to be philosophers of religion, while a lack of belief led others to become scientists? A survey of 1,646 scientists by Rice University sociologist Elaine Howard Ecklund led her to conclude that (from here): 

Ecklund concludes from her research that most scientists do not become irreligious as a consequence of their becoming scientists. “Rather, their reasons for unbelief mirror the circumstances in which other Americans find themselves: they were not raised in a religious home; they have had bad experiences with religion; they disapprove of God or see God as too changeable.” The disproportionately high percentage of nonbelievers among scientists (as compared to the general population) would appear to be the result of self-selection: the irreligious seem more likely to become scientists in the first place.

I’m not a sociologist, so I can’t critique Ecklund’s work. The point is that individual biases don’t necessarily average themselves out over a population of experts, so appealing to lots of authorities isn’t necessarily an improvement.

Authority as a counterexample to the accusation of ignorance

The defender of the Kalam cosmological argument for the existence of God claims that the universe has a beginning. One argument goes as follows:

Premise 1. An actual infinite cannot exist in reality.

Premise 2. An infinite temporal regress of events is an actual infinite.

Premise 3. Therefore, an infinite temporal regress of events cannot exist.

Reasoning with actual infinites requires knowledge of mathematics, specifically transfinite arithmetic. The argument’s best known defender is William Lane Craig.Craig is not a mathematician, and so one might wonder whether he is sufficiently familiar with the relevant mathematics. We all know of arguments that reveal more about the ignorance of the arguer than about the subject at hand.

There are two ways for Craig to counter the accusation that a greater knowledge of mathematics would lead one to reject Premise 1. The long way is to demonstrate his own proficiency in transfinite arithmetic. That would take a while. He discusses the topic at length in his book “The Kalam Cosmological Argument” if you want to take that route. There is a shortcut, however. Craig could provide an example of someone whose mathematical credentials are unquestioned and who affirms Premise 1. Craig can do this, and so usually does so in shortened presentations like debates. The authority is David Hilbert, who was one of the greatest mathematicians of the 20th century and who argued that “the actual infinite is nowhere to be found in reality”.

This is a valid appeal to authority, so long as we are clear on what is being claimed. Obviously, we cannot claim that Premise 1 is true because Hilbert thought so. But we can counter the accusation that anyone who believes Premise 1 is ignorant of mathematics and doesn’t understand the idea of infinity.

(Note well: I’m not defending premise 1. I’m planning a series on the cosmological arguments, so stay tuned. I’m not convinced by “Hilbert’s hotel is metaphysically absurd” style arguments. And, as Jeff Shallit has pointed out, mathematical knowledge of transfinite arithmetic is a necessary but not sufficient qualification as we are dealing with the applicability of mathematics to reality, which is physics. The accusation that “greater knowledge of physics / cosmology / relativity would lead one to reject Premise 1” can also be countered: George Ellis. The main utility of these authorities, I contend, is to take our attention away from the claimers and focus attention on the claims. We won’t get stuck in a useless debate about whether Craig really understands maths.).

Authority and hostile witnesses

A particularly useful form of appealing to authority is the use of a hostile witness. In this context, a hostile witness is one who attests to a fact in the teeth of their own biases. If someone who hates the defendant’s guts nevertheless corroborates his alibi, then this has greater weight as evidence than such corroboration from a friend of the defendant. It works in reverse as well: if the defendant’s loving wife testifies that he was out of the house between 10pm and 1am, knowing that this was the time of the murder, then this is weighty evidence. She has every reason to give him an alibi, and so the most likely reason for her statement is that it is true.

This is one of the reasons that the study of history is not paralyzed by the inevitable bias of those who write history. Is the New Testament useless as a historical record, because its writers were followers of Jesus? Not necessarily, because this bias can be used in our favour. If the gospel writers admit something about Jesus that was an embarrassment to them, then we have good reason to believe that they did not invent this story to suit their own ends.

For example, Mark 13:32 has Jesus saying “But about that day or hour no one knows, not even the angels in heaven, nor the Son, but only the Father”. If we can establish that the early Christians believed that Jesus was divine, then there is a strong bias against inventing a saying of Jesus that says that he didn’t know something. It’s not proof, but it is evidence.

As before, we must be clear about the claim that the authority is supporting. A hostile witness can be used to counter the claim that only those biased in favour of a position believe its claims. I’ve come across this in the context of the fine-tuning of the universe for intelligent life. This subject is so popular with theists that I often encounter the claim that it is the product of Christian apologetics, and believed only by “religious types”. Actually, much has been written on fine-tuning in peer-reviewed scientific journals and I can (and have) give many examples of non-theist physicists who affirm that life-permitting universes are rare in the set of possible universes.

But don’t take my word for it …

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