Silencing Opinion is a 'peculiar evil'

In his celebrated little book, On Liberty, the English philosopher John Stuart Mill argued that silencing an opinion is 'a peculiar evil'. If the opinion is right, we are robbed of the 'opportunity of exchanging error for truth'; and if it's wrong, we are deprived of a deeper understanding of the truth in 'its collision with error'. If we know only our own side of the argument, we hardly know even that; it becomes stale, soon learned only by rote, untested, a pallid and lifeless truth. Mill ...