As I have been going about my rationalist training, I have noticed a fallacy which I can’t find the name of. My aim is to describe it to all you smart people who know more than I do in hopes that someone can give me the proper name for it. If, indeed, I have found something that constitutes as a new fallacy, I’m happy to name it, but I wanted to make sure it really truly doesn’t already exist.

Here’s how it goes:

  • You believe A to be true
  • You are in any of the following situations:

a. “I cannot ask anyone their opinion on A.”

b. “I don’t have something I need in order to ask other’s their opinion on A” (examples of things you might need: time, courage, a clipboard, an intergalactic spaceship etc.)

c. “I haven’t promoted this to conscious attention or questioned the validity of my opinion on A and therefore haven’t even thought to ask anyone their opinion on A"

  • You don’t ask others their opinion on A
  • You assume A to be true based on your one data point

Some examples of this fallacy in action:

The Fermi Paradox (a/b)

Synesthetic people assuming everyone else is synesthetic too (c)

Agender people assuming everyone else has as little regard for the value of gender as they do (b/c)

Lots more examples can be found in the LW post “Other People are Occasionally Rather Weird” and “Being Wrong About Your Own Subjective Experience” as well as the Slate Star Codex post: “What Universal Human Experiences are you Missing Without Realising it?”

In my search for what this fallacy might be called, the closest I’ve gotten to is Extension Neglect, in which one ignores the size of a set. Please let me know in the comments if my fallacy is indeed part of Extension Neglect, if it has another name I don’t know, or if you have a suggestion for what it should be named (assuming it doesn’t already have a match). Thanks!

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This sounds most similar to what LWers call generalizing from one example or the typical mind fallacy and to what psychologists call the false-consensus effect or egocentric bias.

A few comments:

I definitely can relate to a and b, and being stuck because of it. Not sure if there is a name for it.

"Synesthetic people assuming everyone else is synesthetic too" is an example of the typical mind fallacy. Same with agender. Actually we all fall prey to this particular one without realizing it, in one aspect or another.

Not sure how the Fermi paradox is related to the rest of what you said.

I don't see how your examples fit into the Extension neglect fallacy.

Actually we all fall prey to this particular one without realizing it, in one aspect or another.

At least, you do. (With apologies to Steven Brust)

I quite agree with Paperclip Minimizer, you succumbed to the typical mind fallacy even as you talk about the typical mind fallacy, how ironic.

The typical mind fallacy sounds like the best fit so far. Thanks to both Unnamed and shminux for mentioning it.

I think the illusion of validity fits this description.