"Outside the laboratory, scientists are no wiser than anyone else." Sometimes this proverb is spoken by scientists, humbly, sadly, to remind themselves of their own fallibility. Sometimes this proverb is said for rather less praiseworthy reasons, to devalue unwanted expert advice. Is the proverb true? Probably not in an absolute sense. It seems much too pessimistic to say that scientists are literally no wiser than average, that there is literally zero correlation.

But the proverb does appear true to some degree, and I propose that we should be very disturbed by this fact. We should not sigh, and shake our heads sadly. Rather we should sit bolt upright in alarm. Why? Well, suppose that an apprentice shepherd is laboriously trained to count sheep, as they pass in and out of a fold. Thus the shepherd knows when all the sheep have left, and when all the sheep have returned. Then you give the shepherd a few apples, and say: "How many apples?" But the shepherd stares at you blankly, because they weren't trained to count apples - just sheep. You would probably suspect that the shepherd didn't understand counting very well.

Now suppose we discover that a Ph.D. economist buys a lottery ticket every week. We have to ask ourselves: Does this person really understand expected utility, on a gut level? Or have they just been trained to perform certain algebra tricks?

One thinks of Richard Feynman's account of a failing physics education program:

"The students had memorized everything, but they didn't know what anything meant. When they heard 'light that is reflected from a medium with an index', they didn't know that it meant a material such as water. They didn't know that the 'direction of the light' is the direction in which you see something when you're looking at it, and so on. Everything was entirely memorized, yet nothing had been translated into meaningful words. So if I asked, 'What is Brewster's Angle?' I'm going into the computer with the right keywords. But if I say, 'Look at the water,' nothing happens - they don't have anything under 'Look at the water'!"

Suppose we have an apparently competent scientist, who knows how to design an experiment on N subjects; the N subjects will receive a randomized treatment; blinded judges will classify the subject outcomes; and then we'll run the results through a computer and see if the results are significant at the 0.05 confidence level. Now this is not just a ritualized tradition. This is not a point of arbitrary etiquette like using the correct fork for salad. It is a ritualized tradition for testing hypotheses experimentally. Why should you test your hypothesis experimentally? Because you know the journal will demand so before it publishes your paper? Because you were trained to do it in college? Because everyone else says in unison that it's important to do the experiment, and they'll look at you funny if you say otherwise?

No: because, in order to map a territory, you have to go out and look at the territory. It isn't possible to produce an accurate map of a city while sitting in your living room with your eyes closed, thinking pleasant thoughts about what you wish the city was like. You have to go out, walk through the city, and write lines on paper that correspond to what you see. It happens, in miniature, every time you look down at your shoes to see if your shoelaces are untied. Photons arrive from the Sun, bounce off your shoelaces, strike your retina, are transduced into neural firing frequences, and are reconstructed by your visual cortex into an activation pattern that is strongly correlated with the current shape of your shoelaces. To gain new information about the territory, you have to interact with the territory. There has to be some real, physical process whereby your brain state ends up correlated to the state of the environment. Reasoning processes aren't magic; you can give causal descriptions of how they work. Which all goes to say that, to find things out, you've got to go look.

Now what are we to think of a scientist who seems competent inside the laboratory, but who, outside the laboratory, believes in a spirit world? We ask why, and the scientist says something along the lines of: "Well, no one really knows, and I admit that I don't have any evidence - it's a religious belief, it can't be disproven one way or another by observation." I cannot but conclude that this person literally doesn't know why you have to look at things. They may have been taught a certain ritual of experimentation, but they don't understand the reason for it - that to map a territory, you have to look at it - that to gain information about the environment, you have to undergo a causal process whereby you interact with the environment and end up correlated to it. This applies just as much to a double-blind experimental design that gathers information about the efficacy of a new medical device, as it does to your eyes gathering information about your shoelaces.

Maybe our spiritual scientist says: "But it's not a matter for experiment. The spirits spoke to me in my heart." Well, if we really suppose that spirits are speaking in any fashion whatsoever, that is a causal interaction and it counts as an observation. Probability theory still applies. If you propose that some personal experience of "spirit voices" is evidence for actual spirits, you must propose that there is a favorable likelihood ratio for spirits causing "spirit voices", as compared to other explanations for "spirit voices", which is sufficient to overcome the prior improbability of a complex belief with many parts. Failing to realize that "the spirits spoke to me in my heart" is an instance of "causal interaction", is analogous to a physics student not realizing that a "medium with an index" means a material such as water.

It is easy to be fooled, perhaps, by the fact that people wearing lab coats use the phrase "causal interaction" and that people wearing gaudy jewelry use the phrase "spirits speaking". Discussants wearing different clothing, as we all know, demarcate independent spheres of existence - "separate magisteria", in Stephen J. Gould's immortal blunder of a phrase. Actually, "causal interaction" is just a fancy way of saying, "Something that makes something else happen", and probability theory doesn't care what clothes you wear.

In modern society there is a prevalent notion that spiritual matters can't be settled by logic or observation, and therefore you can have whatever religious beliefs you like. If a scientist falls for this, and decides to live their extralaboratorial life accordingly, then this, to me, says that they only understand the experimental principle as a social convention. They know when they are expected to do experiments and test the results for statistical significance. But put them in a context where it is socially conventional to make up wacky beliefs without looking, and they just as happily do that instead.

The apprentice shepherd is told that if "seven" sheep go out, and "eight" sheep go out, then "fifteen" sheep had better come back in. Why "fifteen" instead of "fourteen" or "three"? Because otherwise you'll get no dinner tonight, that's why! So that's professional training of a kind, and it works after a fashion - but if social convention is the only reason why seven sheep plus eight sheep equals fifteen sheep, then maybe seven apples plus eight apples equals three apples. Who's to say that the rules shouldn't be different for apples?

But if you know why the rules work, you can see that addition is the same for sheep and for apples. Isaac Newton is justly revered, not for his outdated theory of gravity, but for discovering that - amazingly, surprisingly - the celestial planets, in the glorious heavens, obeyed just the same rules as falling apples. In the macroscopic world - the everyday ancestral environment - different trees bear different fruits, different customs hold for different people at different times. A genuinely unified universe, with stationary universal laws, is a highly counterintuitive notion to humans! It is only scientists who really believe it, though some religions may talk a good game about the "unity of all things".

As Richard Feynman put it:

"If we look at a glass closely enough we see the entire universe. There are the things of physics: the twisting liquid which evaporates depending on the wind and weather, the reflections in the glass, and our imaginations adds the atoms. The glass is a distillation of the Earth's rocks, and in its composition we see the secret of the universe's age, and the evolution of the stars. What strange array of chemicals are there in the wine? How did they come to be? There are the ferments, the enzymes, the substrates, and the products. There in wine is found the great generalization: all life is fermentation. Nobody can discover the chemistry of wine without discovering, as did Louis Pasteur, the cause of much disease. How vivid is the claret, pressing its existence into the consciousness that watches it! If our small minds, for some convenience, divide this glass of wine, this universe, into parts — physics, biology, geology, astronomy, psychology, and so on — remember that Nature does not know it! So let us put it all back together, not forgetting ultimately what it is for. Let it give us one more final pleasure: drink it and forget it all!"

A few religions, especially the ones invented or refurbished after Isaac Newton, may profess that "everything is connected to everything else". (Since there is a trivial isomorphism between graphs and their complements, this profound wisdom conveys exactly the same useful information as a graph with no edges.) But when it comes to the actual meat of the religion, prophets and priests follow the ancient human practice of making everything up as they go along. And they make up one rule for women under twelve, another rule for men over thirteen; one rule for the Sabbath and another rule for weekdays; one rule for science and another rule for sorcery...

Reality, we have learned to our shock, is not a collection of separate magisteria, but a single unified process governed by mathematically simple low-level rules. Different buildings on a university campus do not belong to different universes, though it may sometimes seem that way. The universe is not divided into mind and matter, or life and nonlife; the atoms in our heads interact seamlessly with the atoms of the surrounding air. Nor is Bayes's Theorem different from one place to another.

If, outside of their specialist field, some particular scientist is just as susceptible as anyone else to wacky ideas, then they probably never did understand why the scientific rules work. Maybe they can parrot back a bit of Popperian falsificationism; but they don't understand on a deep level, the algebraic level of probability theory, the causal level of cognition-as-machinery. They've been trained to behave a certain way in the laboratory, but they don't like to be constrained by evidence; when they go home, they take off the lab coat and relax with some comfortable nonsense. And yes, that does make me wonder if I can trust that scientist's opinions even in their own field - especially when it comes to any controversial issue, any open question, anything that isn't already nailed down by massive evidence and social convention.

Maybe we can beat the proverb - be rational in our personal lives, not just our professional lives. We shouldn't let a mere proverb stop us: "A witty saying proves nothing," as Voltaire said. Maybe we can do better, if we study enough probability theory to know why the rules work, and enough experimental psychology to see how they apply in real-world cases - if we can learn to look at the water. An ambition like that lacks the comfortable modesty of being able to confess that, outside your specialty, you're no better than anyone else. But if our theories of rationality don't generalize to everyday life, we're doing something wrong. It's not a different universe inside and outside the laboratory.

Addendum: If you think that (a) science is purely logical and therefore opposed to emotion, or (b) that we shouldn't bother to seek truth in everyday life, see "Why Truth?" For new readers, I also recommend "Twelve Virtues of Rationality."