

Variant: The problem with the world is that the intelligent people are full of doubts, while the stupid ones are full of confidence.
La duda es uno de los nombres de la inteligencia.
As quoted in Diccionario privado de Jorge Luis Borges (1979) edited by Blas Matamoro
La duda es uno de los nombres de la inteligencia.
Source: Citado en Compromiso con la excelencia. Traducido por Liliana Lutkin. Ediciones Granica S.A., 2000. ISBN 9788475778389, p. 103.
Variant: The problem with the world is that the intelligent people are full of doubts, while the stupid ones are full of confidence.
“Imagination is but another name for super intelligence.”
“If I had 4 fust rate dogs i would name the best one "Doubtful" and the other 3 "Useless."”
Josh Billings: His Works, Complete (1873)
“[Intelligent Design Theory] Creationism by another name.”
http://mikebloomberg.com/en/news/ny_times_bloomberg_on_everything
Intelligent Design Theory
The Freethinker (1970), G.W. Foote & Company, Volume 90, p. 147.
Date unknown
Often paraphrased as "The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts."
Compare: "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." B. Russell, New Hopes for a Changing World (1951). Compare also: "The best lack all conviction, while the worst / Are full of passionate intensity." W. B. Yeats, The Second Coming (1919).
See also: Dunning-Kruger effect, Historical Antecedents https://en.wikipedia.org/wiki/Dunning–Kruger_effect#Historical_antecedents.
1930s, Mortals and Others (1931-35)