The Dunning–Kruger effect is a cognitive bias in which “people reach erroneous conclusions and make unfortunate choices but their incompetence robs them of the metacognitive ability to realize it.” The unskilled therefore suffer from illusory superiority, rating their own ability as above average, much higher than in actuality; by contrast, the highly skilled underrate their abilities, suffering from illusory inferiority.
“In the modern world the stupid are cocksure while the intelligent are full of doubt.”
Bertrand Russel
This is also subject to the lesser-known Samblam Clause wherein if the sum total of all of the person’s doubts revolve...