We recently established a successful Useful Concepts Repository. It got me thinking about all the useless or actively harmful concepts I had carried around for in some cases most of my life before seeing them for what they were. Then it occurred to me that I probably still have some poisonous concepts lurking in my mind, and I thought creating this thread might be one way to discover what they are.
I'll start us off with one simple example: The Bohr model of the atom as it is taught in school is a dangerous thing to keep in your head for too long. I graduated from high school believing that it was basically a correct physical representation of atoms. (And I went to a *good* high school.) Some may say that the Bohr model serves a useful role as a lie-to-children to bridge understanding to the true physics, but if so, why do so many adults still think atoms look like concentric circular orbits of electrons around a nucleus?
There's one hallmark of truly bad concepts: they actively work against correct induction. Thinking in terms of the Bohr model actively prevents you from understanding molecular bonding and, really, everything about how an atom can serve as a functional piece of a real thing like a protein or a diamond.
Bad concepts don't have to be scientific. Religion is held to be a pretty harmful concept around here. There are certain political theories which might qualify, except I expect that one man's harmful political concept is another man's core value system, so as usual we should probably stay away from politics. But I welcome input as fuzzy as common folk advice you receive that turned out to be really costly.
Within my lifetime, the world will end.
This too is a common belief of fundamentalist Christians (though by no means limited to them), and has many of the same effects as the belief that "Within my lifetime, a magic genie will appear that grants all our wishes and solves all our problems." For instance, no one will save for retirement if they think the world will end before they retire. And it's not important to worry about the state of the environment in 50 years, if the world ends in 25.
However this belief has an important distinction from the belief in magic genies. To the extent that the belief the world is going to end is based in actual facts and not superstition, and to the extent that it leads people to take effective action to prevent the world from ending, this belief can be helpful. For instance, one reason the world didn't already end in nuclear war is that many people worked very hard to avoid that fate. On a smaller, not-quite-world-ending scale, Y2K was a non-event because thousands of programmers spent tens, perhaps hundreds-of-thousands of work-years fixing the problem before it could instantiate.
However, if a belief that the world will end leads one to fatalism, and to giving up on planning for or considering the future, then it is equally as harmful as a belief in magic wish-granting genies.
Except, it was a non-event even in those places where this didn't happen.