The value of coherence in science

Guest podcast by Stephan Lewandowsky
(listen to the original audio podcast)

Suppose a bloke drifts up to you and says, “Apples don’t exist”... While your eyebrows are still rising, he adds, “but they grow naturally on trees!”


“Apples don’t exist but they grow naturally on trees?” Surely you wouldn’t trust that bloke with the lives of your children if their future depended on logical coherence.

Now suppose you walk down the street and some other bloke sidles up and says, “The price of sheep is unknown, but I’d buy some now because they are cheap.”

‘Scuse me?

The price of sheep is unknown but they are cheap? No point trusting that bloke with your kids’ lives either, if their future depended on logical coherence.

Now here’s a surprising fact: Your kids’ future, and the future of their kids, very much depends on logical coherence—very much hinges on protecting them and their future from the incoherent claims of so-called climate “skeptics.”

One of the reliable insights of philosophy of science is that scientific knowledge is virtually never incoherent. In science, a hallmark criterion of whether you can possibly be right is whether or not you are coherent. If you are coherent, you might be right. If you are incoherent or contradict yourself, then you are most likely wrong.

The beauty of this is that you don’t even need data or peer-reviewed science to be sure: If an argument is incoherent or mutually contradictory, then you can be fairly confident that it is wrong or stated for entertainment purposes only.

What does this have to do with so-called climate “skeptics?”


Because the sum total of so-called “skeptic” arguments is an incoherent muddle of contradictions.

On a Monday morning your resident “skeptic” might tell you that global warming does not exist. On the Monday afternoon, she may tell you that the warming is all natural, just the same way that non-existent apples grow on trees.

Nothing this incoherent can be right.

And on Tuesday, a so-called “skeptic” may drift into town and make claims about the temperature record not being accurate. He might also assure you that there is nothing to worry about because it hasn’t been warming in the last 23 days anyhow. So the sheep are cheap but no one knows their price.

Nothing this incoherent can be right.

By Wednesday morning, your excited “skeptic” may have invented the possibility that the sun is causing global warming, and by afternoon tea time it might be cosmic rays, or El Niño, or Inspector Clouseau or whatever.

Now, you may find it hard to believe that anyone could be so muddled, but in fact, it takes little effort to go to a “skeptic” website and dig out dozens if not hundreds such contradictions. Hundreds of instances in which apples were said not to exist but then happily grow on trees. Hundreds of clear indications that this so-called “skepticism” amounts to little more than muddled mutterings.

There is, of course, a coherent alternative. It is the coherent and overwhelmingly supported scientific fact that the Earth’s climate is warming and that humans are largely responsible for it. That is coherent, backed by peer-reviewed science, and endorsed by all major scientific organizations in the world.


This 3-minute podcast was previously “blog reviewed” here on, and I wish to thank those who contributed to improving this piece through their thoughtful and detailed comments. For new readers, please bear in mind that the podcasts are spoken and hence must be understandable by listening alone—though obvious, this is no trivial matter because it mandates simplifications that would be unnecessary in writing.

For aficionados of philosophical esoterica, a theory of ontology known as Meinongianism, after Alexius Meinong, holds that even non-existent entities (e.g., Santa Claus) have some type of “being” simply because one can think about them, which in turn means that they may be thought to have properties (e.g., living at the North Pole). This position has been critiqued by several philosophers, Bertrand Russell foremost among them, and I am not aware of it having any influence on contemporary science.

I thank my philosopher colleague Dr Nic Damnjanovic for helpful discussions about the issues raised in this podcast.

There will be a post forthcoming on this website in the near future that explicitly enumerates contradictions and incoherent statements made by “skeptics.” In the meantime, you may wish to check Eli Rabbett’s earlier analysis of contradictions.

Posted by Stephan Lewandowsky on Wednesday, 6 October, 2010

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