Critias (l. c. 460-403 BCE) was an Athenian politician, poet, and playwright, and one of Socrates‘ followers:
“It’s terrible when someone who’s stupid thinks he’s intelligent.
δεινὸν δ’ ὅταν τις μὴ φρονῶν δοκῇ φρονεῖν.” (h/t)
“those with limited knowledge in a domain suffer a dual burden: Not only do they reach mistaken conclusions and make regrettable errors, but their incompetence robs them of the ability to realize it.”
Kruger, J., & Dunning, D. (1999). Unskilled and unaware of it: How difficulties in recognizing one’s own incompetence lead to inflated self-assessments. Journal of Personality and Social Psychology, 77(6), 1121–1134. https://doi.org/10.1037/0022-3514.77.6.1121