Sigmund Freud Quotes about Doubt
Only the real, rare, true scientific minds can endure doubt, which is attached to all our knowledge.
Sigmund Freud (2014). “Beyond the Pleasure Principle”, p.14, Courier Corporation
Sigmund Freud, James Strachey, Anna Freud, Carrie Lee Rothgeb (1961). “The Standard Edition of the Complete Psychological Works of Sigmund Freud”
"Studies on Hysteria". Book by Sigmund Freud and Josef Breuer, as translated by Nicola Luckhurst (2004), 1895.