It is the duty of every man, ...

It is the duty of every man, as far as his ability extends, to detect and expose delusion and error.
It is the duty of every man, as far as his ability extends, to detect and expose delusion and error.

More phrases

All the great things are simple, and many can be expressed in a single word: freedom, justice, honor, duty, mercy, hope.
I know but one freedom and that is the freedom of the mind.
 Antoine de Saint-Exupéry
Freedom is not worth having if it does not connote freedom to err.
The amount of happiness that you have depends on the amount of freedom you have in your heart.
 Thích Nhất Hạnh
Without freedom of thought, there can be no such thing as wisdom - and no such thing as public liberty without freedom of speech.

Quotes from the same author

A long habit of not thinking a thing wrong gives it a superficial appearance of being right.
The World is my country, all mankind are my brethren, and to do good is my religion.
The most formidable weapon against errors of every kind is reason.
Arms, like laws, discourage and keep the invader and plunderer in awe and preserve order.
The balance of power is the scale of peace. The same balance would be preserved were all the world not destitute of arms, for all would be alike; but since some will not, others dare not lay them aside ... Horrid mischief would ensue were one half the world deprived of the use of them ... the weak will become prey to the strong.