Bertrand Russell book Sceptical Essays
Source: 1920s, Sceptical Essays (1928), Ch. 12: Free Thought and Official Propaganda http://books.google.com/books?id=9tQsg5ITfHsC&q="It+is+clear+that+thought+is+not+free+if+the+profession+of+certain+opinions+makes+it+impossible+to+earn+a+living"&pg=PA126#v=onepage