Censorship: the cyclical suppression, banning, expurgation, or editing by an individual, institution, group or government that enforce or influence its decision against members of the public -- of any written or pictorial materials which that individual, institution, group or government deems obscene and "utterly without redeeming social value," as determined by "contemporary community standards."
Stone divides censorship into three types:
Historically, censorship has been conducted by three entities: the government, private individuals or groups, and religions. But it also can involve self-censorship. Three frequent rationalizations for censorship are:
But the the root motivation for censorship is always the same: Fear that "the expression, if not curtailed, will do harm to individuals in its audience or to society as a whole." (Academic American)
Societies most confident of their principles and of the loyalty of their members have allowed the greatest freedom from censorship. "In societies whose values have not been fully accepted by their people or whose leadership rests on shaky foundations, the heaviest hand of censorship has fallen. The relative prevalence of censorship is one of the features that has most distinguished autocratic from democratic societies." (Academic American)
"Freedom of expression is not merely a personal liberty but is an essential part of the mechanism of government by the people. Their right to vote is not enough by itself to give them effective control of official actions and policies. They must also be able to take part in the formation of public opinion by engaging in vigorous and wide- ranging debate on controversial matters." (Encylopedia Americana) When government censors peaceable opposition in the short run, it risks the long-run danger of violent opposition or revolution. (Encyclopedia Americana; Encyclopedia of the Social Sciences)
New means of communication, however, have always called for new measures of control. "This was true of the printing press, the cinema, the radio and television, the establishment of public libraries, the development of textbooks for school use and the introduction of the paperback book and the comics." And it is true of the Internet. (Encyclopedia Britannica)
But it's also true that "every censorship produces a technique of evasion as well as a technique of administration." And "it is a notorious fact that censorship or the threat of censorship may make the fortune of a book or play which might otherwise have failed to win public attention." (Encyclopedia of the Social Sciences)