The Dunning-Kruger effect,
named after David Dunning and Justin Kruger of Cornell University, occurs where people fail to adequately assess their level of competence — or specifically, their incompetence — at a task and thus consider themselves much more competent than everyone else. This lack of awareness is attributed to their lower level of competence robbing them of the ability to critically analyse their performance, leading to a significant overestimate of themselves. Put more crudely, they're too stupid to realize they're stupid.
The inverse also applies: competent people tend to underestimate their ability compared to others; this is known as impostor syndrome.
If you have no doubts whatsoever about your brilliance, you could just be that damn good. On the other hand...
“”One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision.
|—Bertrand Russell, The Triumph of Stupidity|
The idea that people who don't know enough also don't know enough to realise that they don't know enough ("Dunning-Kruger effect" is so much simpler to get your tongue around) isn't particularly new. The Bertrand Russell quote is from the mid 1930s, and even earlier, Charles Darwin, in The Descent of Man in 1871, stated "ignorance more frequently begets confidence than does knowledge." Even back in ancient Greece, Plato's Apologyattributed to Socrates the quote at the top, which today is often summed up as, roughly, "the wisest people know that they know nothing."
In his 1996 book Rush Limbaugh is a Big Fat Idiot, Al Franken described the phenomenon of "pseudo-certainty" which was rampantly being displayed by pundits and politicians such as Rush Limbaugh and Newt Gingrich, who would use "common sense" as the basis for their confidently-made assertions, but without actually backing them up with time-consuming research or pesky facts. Franken prefers the term "being a fucking moron."
From Rational Wiki