Bertrand Russell quote.

"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts."

This popular quote attributed to Bertrand Russell has no established references as such, but is considered to be a paraphrased version of the following:

"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'.

And another similar statement of Bertrand Russell is:

"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." Bertrand Russell, New Hopes for a Changing World, 1951.

Now, a similar quote from Yeats:

"The best lack all conviction, while the worst Are full of passionate intensity." - William Butler Yeats, The Second Coming, 1919.

And a similar one attributed to another author (this one is unverified yet):

"The problem with the world is that the intelligent people are full of doubts, while the stupid ones are full of confidence."

Charles Bukowski.