Plato argued his ideal city needed one founding myth everyone had to believe
In the Republic, Plato has Socrates propose a 'noble lie': a myth telling citizens they were born from the earth itself, with different metals — gold, silver, bronze — mixed into their souls to mark which class they belong to. Believing it, Socrates argues, would bind citizens together and make them accept the city's social structure as natural rather than imposed. The phrase has since become shorthand for any beneficial falsehood a society is told to hold it together.