
We can never be sure that the opinion we are endeavouring to stifle is a false opinion; and if we were sure, stifling it would be an evil still.
On Liberty - Página 34 http://books.google.com.br/books?id=AjpGAAAAcAAJ&pg=PA34, John Stuart Mill - John W. Parker and son, 1859, 207 páginas
On Liberty