We cannot have a society half slave and half free; nor can we have thought half slave and half free. If we create an atmosphere in which men fear to think independently, inquire fearlessly, express themselves freely, we will in the end create the kind of society in which men no longer care to think independently or to inquire fearlessly.

Henry Steele Commager (1902-1998) American historian, writer, activist

“What Ideas Are Safe?” Saturday Review (1949-11-05)
    (Source)

Collected in Freedom and Order (1966).