"Any test that turns on what is offensive to the community's standards is too loose, too capricious, too destructive of freedom of expression to be squared with the First Amendment. Under that test, juries can censor, suppress, and punish what they don't like, provided the matter relates to "sexual impurity" or has a tendency "to excite lustful thoughts." This is community censorship in one of its worst forms. It creates a regime where, in the battle between the literati and the Philistines, the Philistines are certain to win."