No One Knows:

Since "obscenity" cannot be precisely defined, it follows that there can be no agreement as to what it is. Opinions vary not only from period to period but from country to country. The former fact is illustrated by the frequent lifting of the ban on an obscene publication in subsequent years. For instance, Shaw's "Mrs. Warron's Profession", and "The Showing Up of Blanco Posnet", Sophocles' "Oedipus Rex" (in translation), Granville Barker's "Waste", Wilde's "Salome", Strindberg's "Miss Julio", Van Druten's "Young Woodley", O'Neill's "Desire Under the Elms", Pirandello's "Six Characters", Lawrence's "Rainbow", Joyce's "Ulysses", as well as several others, were at one time forbidden publication or sale, only to be freed from the ban at a later period. An interesting illustration of the second fact - the difference of opinion in different countries - is the fate of the "Well of Loneliness", which was banned in Britain but not in the United States of America, and Walt Whitman's "Leaves of Grass" with which the reverse happened. A charge was actually brought against the "Well of Loneliness" in America but it was unsuccessful. The fate of "Ulysses" is another example. Banned in both America and Britain when it was first published, it was admitted into the former country following the famous judgement of Judge Woolsey in 1934. Not until 1938 was a limited edition brought out publicly by a British firm. "The obscenity of to-day", it has been said, "will be the propriety of tomorrow". The reference, of course, is to the "obscenity" in books with a serious purpose, like "Ulysses" (described by Judge Woolsey as "a sincere and serious attempt to devise a new literary method for the observation of mankind"). It does not include porno graphic books.