Bryan Caplan  

"All Theories Are False"

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I can't tell you how many times natural and social scientists have solemnly told me, "All theories are false."  Their "proof" usually amounts to the solitary example of Newtonian physics, proven false by Einsteinian physics.  But if you're patient, they eventually just say, "Look, no theory perfectly fits the facts.  That makes them all false."

My reply: You're right if "true" means true to an infinite number of decimal places in all conceivable circumstances.  But that's a ridiculous standard of truth.  In ordinary language, a statement is true as long as the world lies inside a range under normal conditions.

Ex: If a farmer tells me that town is 5 miles away, I don't call him a liar if the actual distance is 4.932764 miles.  And I don't call him a liar if, as the crow flies, the town is only 4.167467 miles away.  When you roll down your car window and ask for the distance, it's understood that you aren't asking for the distance by chopper or subterrene.  Of course, if you specified "exactly 5 miles" or "under all conceivable conditions," or "always" you're holding yourself up to much higher standards. 

While we're on the subject, I might as well dispose of a related fallacy: "Claims cannot be proven true, only proven false."  This is often correct if you're making universal claims, like "All X are Y," (though even that might be proven true if the X's are narrowly defined).  But for existence claims, like "Some X are Y," the opposite holds: You can prove the claim true, but cannot prove it false.

What are sophistries about the falsity and unprovability of everything so popular?  I think the main motivation behind these claims is what Tyler calls "mischievousness."  Some thinkers take perverse delight in declaring that everyone is wrong and nothing can be proven.   It allows them to rhetorically expropriate rival meritorious thinkers in one fell swoop without making enemies with anyone in particular.  Don't let them get away with it.


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COMMENTS (17 to date)
jenizaro writes:

Well, you are talking of two different things here. You begin referring to a perfectly reasonable epistemological stand (that I BTW share: all theories are false) and conclude equating it with the less nice hobby of cynics and relativists.

Any non-naive conception of what "true" means forces you to accept that it is impossible to establish an exact correspondence between your ideas about the world and the world itself, if only because your perception about the world itself is mediated by your senses, which may distort the true properties of the world itself.

This of course doesn't mean you can't pursue theories that are useful: http://en.wikipedia.org/wiki/Instrumentalism.

PaulG writes:

And don't forget "you can't prove a negative", which is easily disposed of by just framing a so-called "positive claim" as a negative. "I have something in my pocket" = "My pocket is not empty."

anonymous writes:

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greenish writes:

Newton was right, full stop. If he had ever claimed "this is a total description of reality", then he would have been wrong. If he had ever claimed "this is an accurate description up to the limits of available observations as far as I am aware of", he would have been making a true, but obvious, statement. And Newton was smart enough to grasp the problem that when you have a force which acts between every pair of particles in the universe, everything you do is approximate anyway.

malavel writes:

You can't disprove statements either because that would mean that you could prove that some other statement is true (that would prove that the original statement is false).

woupiestek writes:

"not empty" is a double negative in some sense. Mathematically, proving that your pocket is not empty is easier than proving you have something in your pocket.

SheetWise writes:

These types of disagreements are what make markets so much fun -- and why markets enrich us all.

Debate is cheap -- put your money where your mouth is.

I know this sounds debasing to some elitists. I spent my youth as a gambler, and made all of my money gambling for several years. In the process, I refined my knowledge of mathematics and the proper application of theory. I relied on Epstein, Thorpe, Kelly, and many others.

Go forward several decades and I now get the perspective of Talib, who confirms my knowledge of domesticated probabilities and introduces me to their misapplication in economics.

A lot of the reason I keep coming here is because I know that markets work, micro rocks, macro is voodoo, and markets work.

Simply ask a bunch of macro adherents to participate in a prediction market with their own money -- and don't break your neck looking down to see where they peg their confidence.

Tom Myers writes:

As Isaac Asimov put it (see Asimov - The Relativity of Wrong)


when people thought the earth was flat, they were wrong. When people
thought the earth was spherical, they were wrong. But if you think
that thinking the earth is spherical is just as wrong as thinking the
earth is flat, then your view is wronger than both of them put together.

Chris H writes:

This is not a very useful way of looking at the work that scientists like Newton do.

A better question is "is the model that Newton proposed useful?" and the answer is yes. Through extensive testing we learn when a particular model corresponds closely enough to reality to be useful as long as we use it within those tested bounds.

Norman writes:

While your argument is valid as far as it goes, I think there is some benefit to the position that no theory is true. Once we say something is 'true' we develop an emotional attachment to the thing, often to the extent that we are unwilling to consider any other possibilities.

While this is fine enough in issues of philosophy / worldview (albeit annoying for those who disagree with us), it is fundamentally opposed to the idea of scientific advancement. We see far too much holding on to 'truth' in science today, in the sense that anyone offering an alternative theory (and its corresponding testable predictions) is laughed off the podium.

William writes:

jenizaro nails right out of the box. But I'll add on anyway.

You are simply misunderstanding what the statement "all theories are false" means, and the fact that some people who make this claim don't understand it or can't explain it either doesn't make it less true.

"All theories are false" is an acknowledgment that the elements of our models are not the elements of reality itself. The consequence of this is that we must be careful in extending any theory into situations for which it was not designed.

Probably the most obvious examples of this problem come, strangely enough, from economics. Normally, economists really do care about increasing GDP, because this thing we call "GDP" seems to match pretty well with things that people desire and pursue. So, my theoretical conclusion is, increasing GDP is good.

But now think about Robert Higgs' commentary on government spending during WWII. The US Government more or less forced people to produce certain goods at certain prices. Measured GDP went up. So, were people better off? No, because the element of coercion changed what GDP means.

So is it false that higher GDP is good? No, but it just means that this conclusion is sensitive to the concept of GDP contained in your model. You can't just change important concepts in the model and assume that your old conclusions still apply.

That's what "all theories are false" means. They are designed for special circumstances and certain situations. Push them hard enough, and they will fall apart.

agnostic writes:

This is what model comparison in statistics is for.

The model is rewarded for its fit to the data, but is penalized for the number of free parameters.

So, all models are false, but some get more insight for their complexity buck. And it's only once we've done better on this score that we junk the old model.

Alan Watson writes:

As I understand the history (which I'm pretty sure is somewhat wrong, but I hope considerably more right than wrong), the followers of Rene Descartes initially rejected Newton's law of gravitation because it did not explain how two masses could influence each other without actually touching. Newton's response was something like "I don't know how it works, but it works". In other words, his model was valuable because it was predictive even though he knew it was not a complete explanation. In this case the Cartesians' motivation was not mischievousness, but some combination of rational skepticism and tribal instinct.

Over the subsequent centuries the English greater emphasis on empiricism seems to have been more productive than the French greater emphasis on rationality, even though any understanding of reality must consist of both. Perhaps our second-tier thinkers, outcompeted by their scientific superiors and looking for an alternative path to success, are increasingly tempted toward the French style of thought.

Chris writes:

I'm wondering why Arnold Kling would disagree with you!

noahpoah writes:

I would take the agnostic position that we can't ever know whether theories are true or not, but that this doesn't matter.

Theories are evaluated according to a variety of criteria (e.g., empirical scope, compatibility with related theories, internal consistency, etc...), none of which are coextensive with truth. Individual scientists likely believe in the truth or falsity of this or that theory, but in arguing for or against one or another, they employ truth-irrelevant criteria.

Alex J. writes:

The flip side of taking perverse delight in proving others wrong is having a morbid fear of being proven wrong.

Michael F. writes:

"All theories are false," seems contradictory to me, akin to the story about a piece of paper on which is written on one side "the statement on the other side of this paper is false" while the other side contains the phrase "the statement on the other side of this paper is true."

More sensible, I think, is the idea that, in science, all theories are falsifiable, or ought to be, in order to qualify as scientific theories. The comment goes to the empirical nature of science, and empiricism involves prediction and evaluation.

Consider theology, by way of contrast, which does not involve theories. Theology is based on faith: beliefs not subject to empirical test (though many have tried) and the evaluation of the truth value of religious belief is simply not the same as in science.

The idea that all theories are false seems to me to be a theory. The idea that all theories are falsifiable (or testable empirically) is a definition.

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