Brian Armstrong

How to Tell What's Bullshit and What's True - Part 1

I’ve been shocked lately to notice how many of my friends (who are otherwise very intelligent) believe things which are totally false.

It’s not just my friends. A remarkably large percentage of the population (and gasp maybe even you) believe some things like:

  • You can catch a cold from going outside with wet hair.

  • The position of the planets at your birth changes your personality (Astrology).

  • Shaving causes hair to grow back thicker/faster.

  • More babies are born on a full moon.

  • Microwaving plastic food containers releases cancer causing chemicals

Sorry, but those are unlikely to be true.

There are hundreds of these myths floating around in conventional wisdom and email inboxes, and I think it’s important to understand how to be a rational human being in today’s world.

How do you decide what’s true and what’s not?

The first lesson here is to realize that just because something intuitively SEEMS true, does not mean you should believe it. Our brains have the remarkable ability to learn from the world around us, but they can also play tricks on us.

For example, it’s very INTUITIVE to our brains that if you dropped a 100lb. ball and a 10lb. ball at the same time, the heaver one would hit the ground first. But thanks to Isaac Newton Galileo, we now know that to be false.

Similarly, it’s very INTUITIVE for our brains to think of the earth as the center of the solar system with the sun revolving around it. It “just looks” that way because the sun comes up in the morning and goes across the sky. Copernicus eventually convinced the world the sun was at the center of the solar system.

By the way, both of these ideas were met with ridicule (and sometimes worse) when they came out. Why? It upset people because it just didn’t SEEM right. It broke their view of the world, and people get upset when you challenge their closely held beliefs.

My point here is simple: just because something SEEMS true isn’t a good reason to believe it.

Some Common Mistakes

  1. Using Anecdotal Evidence This is the most common one I see. It basically means using a personal experience or observation to draw a much larger conclusion. For example, “my grandfather smoked a pack a day and lived to be 95, smoking isn’t dangerous!”. This isn’t evidence at all because it’s not a controlled study with a large enough sample size to draw any reasonable conclusion.

To prove this to yourself, take something you know to be true. For example: eating tons of unhealthy food makes you fat. Now ask yourself if there is any specific case where this is not true? Well, yes, there is probably SOME lucky person out there who eats a ton of food and isn’t fat. Now if you knew nothing about food and had heard this one story (anecdote), it could be used (incorrectly) as evidence to suggest that eating lots of food does NOT make you fat.

Sure, in this case you would know better, but what about in more complex subjects like medicine or health? Hopefully you can see the danger of anecdotal evidence.

Opinions, observations, and stories are no substitute for a carefully controlled experiment (more on this later).

  1. Assuming Correlation Proves Causation People also make the mistake of assuming that because A happened, and then B happened, A must have CAUSED B. This is also known as the post-hoc fallacy.

Example: Kids are listening to rap music now (playing more video games, smoking pot, etc - take your pick) and violence is up, obviously the rap music caused it. Well, maybe it did and maybe it didn’t. But merely noticing that when one went up the other went up proves nothing on it’s own. Maybe B caused A, the violence caused the rap music. Or maybe they aren’t related at all. Stating a correlation proves nothing about causation.

As stated on Skeptic.com…

You have a cold, so you drink fluids and two weeks later your cold goes away. You have a headache so you stand on your head and six hours later your headache goes away. You put acne medication on a pimple and three weeks later the pimple goes away. You perform some task exceptionally well after forgetting to bathe, so the next time you have to perform the same task you don’t bathe. A solar eclipse occurs so you beat your drums to make the gods spit back the sun. The sun returns, proving to you the efficacy of your action.

Only a controlled study can show causation, not correlation on it’s own.

  1. Thinking It’s True Because It Can’t Be Proved False This is called an argument from ignorance or logical fallacy, where you assume that something is true just because it can’t be proved false.

It can also take the opposite form where you assume something is false just because it can’t be proved true.

Example: “You can’t prove God doesn’t exist, so God must exist.”

You can, again, prove to yourself that this isn’t evidence at all. Some things are just impossible to prove false. For example, what if I said there is a teapot orbiting the sun somewhere in our solar system. This is ridiculous of course, because even if you looked long and hard for it, I could always say well you just haven’t found it yet…space is a big place! It is impossible to disprove, and clearly this provides no evidence that a teapot does in fact orbit the sun.

Part One Summary

When you hear people say one of these, it should set off a BS alarm off in your head. Here are some phrases to watch out for:

“I know it’s real because it happened to me” (Anecdotal) “Everyone I talked to said it’s true” (Anecdotal) “Of course it happened after [BLANK] came in!” (Correlation/Causation) “Well you can’t prove that it doesn’t!” (Argument from ignorance)

So far this article has mostly talked about what NOT to do.

In part two I’ll talk about what TO do: the CORRECT way to prove something, how to quickly find the truth for yourself, and a study on pigeons which will blow your mind.

UPDATE: Here is a link to part 2.

Until next time, keep breaking free! Brian Armstrong

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