How to use an "argument from authority"

I spent the holidays playing with the video animation software. As a side-effect, I produced this little video.



If you'd rather read than listen, here's the complete voiceover:

It has become a popular defense of science deniers to yell “argument from authority” when someone quotes an experts’ opinion. Unfortunately, the argument from authority is often used incorrectly.

What is an “argument from authority”?

An “argument from authority” is a conclusion drawn not by evaluating the evidence itself, but by evaluating an opinion about that evidence. It is also sometimes called an “appeal to authority”.

Consider Bob. Bob wants to know what follows from A. To find out, he has a bag full of knowledge. The perfect argument would be if Bob starts with A and then uses his knowledge to get to B to C to D and so on until he arrives at Z. But reality is never perfect.

Let’s say Bob wants to know what’s the logarithm of 350,000. In reality he can’t find anything useful in his bag of knowledge to answer that question. So instead he calls his friend, the Pope. The Pope says “The log is 4.8.” So, Bob concludes, the log of 350,000 is 4.8 because the Pope said so.

That’s an argument from authority – and you have good reasons to question its validity.

But unlike other logical fallacies, an argument from authority isn’t necessarily wrong. It’s just that, without further information about the authority that has been consulted, you don’t know how good the argument it is.

Suppose Bob hadn’t asked the Pope what’s the log of 350,000 but instead he’d have asked his calculator. The calculator says it’s approximately 5.544.

We don’t usually call this an argument from authority. But in terms of knowledge evaluation it’s the same logical structure as exporting an opinion to a trusted friend. It’s just that in this case the authority is your calculator and it’s widely known to be an expert in calculation. Indeed, it’s known to be pretty much infallible.

You believe that your friend the calculator is correct not because you’ve tried to verify every result it comes up with. You believe it’s correct because you trust all the engineers and scientists who have produced it and who also use calculators themselves.

Indeed, most of us would probably trust a calculator more than our own calculations, or that of the Pope. And there is a good reason for that – we have a lot of prior knowledge about whose opinion on this matter is reliable. And that is also relevant knowledge.

Therefore, an argument from authority can be better than an argument lacking authority if you take into account evidence for the authority’s expertise in the subject area.

Logical fallacies were widely used by the Greeks in their philosophical discourse. They were discussing problems like “Can a circle be squared?” But many of today’s problems are of an entirely different kind, and the Greek rules aren’t always helpful.

The problems we face today can be extremely complex, like the question “What’s the origin of climate change?” “Is it a good idea to kill off mosquitoes to eradicate malaria?” or “Is dark matter made of particles?” Most of us simply don’t have all the necessary evidence and knowledge to arrive at a conclusion. We also often don’t have the time to collect the necessary evidence and knowledge.

And when a primary evaluation isn’t possible, the smart thing to do is a secondary evaluation. For this, you don’t try to answer the question itself, but you try to answer the question “Where do I best get an answer to this question?” That is, you ask an authority.

We do this all the time: You see a doctor to have him check out that strange rush. You ask your mother how to stuff the turkey. And when the repair man says your car needs a new crankshaft sensor, you don’t yell “argument from authority.” And you shouldn’t, because you’ve smartly exported your primary evaluation of evidence to a secondary system that, you are quite confident, will actually evaluate the evidence *better* than you yourself could do.

But… the secondary evidence you need is how knowledgeable the authority is on the topic of question. The more trustworthy the authority, the more reliable the information.

This also means that if you reject an argument from authority you claim that the authority isn’t trustworthy. You can do that. But it’s here’s where things most often go wrong.

The person who doesn’t want to accept the opinion of scientific experts implicitly claims that their own knowledge is more trustworthy. Without explicitly saying so, they claim that science doesn’t work, or that certain experts cannot be trusted – and that they themselves can do better. That is a claim which can be made. But science has an extremely good track record in producing correct conclusions. Questioning that it’s faulty therefore carries a heavy burden of proof.

So. To use an argument from authority correctly, you have to explain why the authority’s knowledge is not trustworthy on the question under consideration.

But what should you do if someone dismisses scientific findings by claiming an argument from authority?

I think we should have a name for such a mistaken use of the term argument from authority. We could call it the fallacy of the “omitted knowledge prior.” This means it’s a mistake to not take into account evidence for the reliability of knowledge, including one’s own knowledge. You, your calculator, and the pope aren’t equally reliable when it comes to evaluating logarithms. And that counts for something.