The Golden Rule of Knowledge

"Prīmum cognōsce tuam ignōrantiam."

"First know of your ignorance." 

	“…nihil se scire dicat nisi id ipsum, eoque praestare ceteris quod illi quae nesciant scire se putent, ipse se nihil scire, id unum sciat, ob eamque rem se arbitrari ab Apolline omnium sapientissimum esse dictum quod haec esset una omnis sapientia, non arbitrari se scire quod nesciat.” “…to assert that he knows nothing except the fact of his own ignorance, and that he surpassed all other people in that they think they know things that they do not know but he himself thinks he knows nothing, and that he believed this to have been the reason why Apollo declared him to be the wisest of all men, because all wisdom consists solely in not thinking that you know what you do not know.”  – Cicero, Academic a, I, 4 (45 BCE)
	"The fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt." – Bertrand Russell, Mortals and Others (1931-35)
	"A man's got to know his limitations." – "Dirty Harry" Callahan, Magnum Force (1973)
	"People tend to hold overly favorable views of their abilities in many social and intellectual domains. The authors suggest that this overestimation occurs, in part, because people who are unskilled in these domains suffer a dual burden: Not only do these people reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the metacognitive 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.