“Truly it is a sad thing for a people, as for a man, to fall into Scepticism, into dilettantism, insincerity; not to know Sincerity when they see it. For this world, and for all worlds, what curse is so fatal?”
1840s, Heroes and Hero-Worship (1840), The Hero As King
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Thomas Carlyle 481
Scottish philosopher, satirical writer, essayist, historian… 1795–1881Related quotes

“That's what show business is--sincere insincerity.”
Quoted in The Observer (12 June 1977)
Source: Organization and Management: Selected Papers (1948), p. 11

As quoted in Malcolm X: The Seeker of Justice (2003); also quoted at "Malcolm X - An Islamic Perspective" http://www.colostate.edu/Orgs/MSA/find_more/m_x.html
Attributed
Context: In the past, yes, I have made sweeping indictments of all white people. I will never be guilty of that again — as I know now that some white people are truly sincere, that some truly are capable of being brotherly toward a black man. The true Islam has shown me that a blanket indictment of all white people is as wrong as when whites make blanket indictments against blacks.

Source: The Seth Material (1970), p. 274
Context: It is wrong to curse a flower and wrong to curse a man. It is wrong not to hold any man in honor, and it is wrong to ridicule any man. You must honor yourselves and see within yourselves the spirit of eternal vitality. If you do not do this, then you destroy what you touch. And you must honor each other individual also, because in him is the spark of eternal vitality. When you curse another, you curse yourselves, and the curse returns to you. When you are violent, the violence returns... I speak to you because yours is the opportunity [to better world conditions] and yours is the time. Do not fall into the old ways that will lead you precisely into the world that you fear.

“It's a curse to see all that might happen but never know what will.”
Source: Challenger Deep

Voltaire (1916)

2010s, 2016, September, First presidential debate (September 26, 2016)