“Censorship is the child of fear and the father of ignorance.”

Clinging to the Wreckage : A Part of Life (1982), p. 183

" On Prejudice http://www.blupete.com/Literature/Essays/Hazlitt/Prejudice.htm"
Men and Manners: Sketches and Essays (1852)

The Drowned and the Saved (1986)
Context: In countries and epochs in which communication is impeded, soon all other liberties wither; discussion dies by inanition, ignorance of the opinion of others becomes rampant, imposed opinions triumph. The well-known example of this is the crazy genetics preached in the USSR by Lysenko, which in the absence of discussion (his opponents were exiled to Siberia) compromised the harvests for twenty years. Intolerance is inclined to censor, and censorship promotes ignorance of the arguments of others and thus intolerance itself: a rigid, vicious circle that is hard to break.

"The Ballad of the Children of the Czar" http://www.poemhunter.com/poem/the-ballad-of-the-children-of-the-czar/
Selected Poems: Summer Knowledge (1959)

Cicero
Misattributed

Source: Parable of the Talents (1998), Chapter 12 (p. 225)

The Liberty of Man, Woman and Child (1877)
Context: There is no slavery but ignorance. Liberty is the child of intelligence.
The history of man is simply the history of slavery, of injustice and brutality, together with the means by which he has, through the dead and desolate years, slowly and painfully advanced.

Source: Moby-Dick or, The Whale

Cults, Sects and Questions (c. 1979)