Cunningham's Law: "the best way to get the right answer on the internet is not to ask a question; it's to post the wrong answer."
The concept is named after Ward Cunningham, the inventor of wiki software. According to Steven McGeady, the law's author, Wikipedia may be the most well-known demonstration of this law.
Cunningham's Law can be considered the Internet equivalent of the French saying "prêcher le faux pour savoir le vrai" ("preach the falsehood to know the truth"). Sherlock Holmes has been known to use the principle at times (for example, in The Sign of the Four.) In "Duty Calls," ("Someone is wrong on the Internet") xkcd references a similar concept.Cunningham's Law | Wikimedia
While not an actual law, Cunningham's Law does make for a nice tangent to those moments when wrong answers are the only answers available at that moment, and one must power forward knowing the answer clutched in their grasp is 100% wrong, like this girl who resignedly reveals a portrait sketch of her parents:
Kudos to mom for holding that laugh in, and pivoting with a Mr. Poopy Butthole "Ohhhhhh" before explaining that "Daddy don't know what he's doing anyway. That's how you say 'that's a great drawing' in French."
Then there's Torio Van Grol, who learned what an Affogato was by winging it with an Avocado: