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 made this remark in the early 1930s amid political extremism, mass propaganda, and economic crisis between the world wars. As a public intellectual committed to rational inquiry and liberal education, Russell worried that modern media and ideological movements rewarded loud certainty over careful thought. The line appears in an essay reflecting on the social consequences of opinion-formation in democratic societies, where complex issues are often reduced to slogans and where expertise can be drowned out by confident ignorance. Russell’s broader aim was to defend intellectual humility and critical thinking as civic virtues in an age increasingly shaped by mass persuasion.

Russell contrasts two psychological tendencies: the unreflective person’s overconfidence and the thoughtful person’s awareness of complexity and fallibility. The “stupid” are “cocksure” because they lack the knowledge needed to recognize uncertainty; the “intelligent” doubt because they can see competing evidence, hidden assumptions, and the limits of what can be proved. The quote is not merely an insult but a warning about public life: when certainty becomes a substitute for understanding, societies may elevate demagogues and punish nuance. Russell implies that healthy judgment requires epistemic humility—confidence proportionate to evidence, and doubt where evidence is incomplete.

1) "The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts." 2) "The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt."