All writers engage with Shakespeare at some point in their careers, whether it be to adapt, imitate, criticize, defend, or admire him. Elizabeth Barrett Browning uses Hamlet to support her belief in the superiority of literary activity above all other activities, while George Sand's Hamlet essay is inspired by a performance of the title role by William Macready. Oscar Wilde criticizes Shakespeare for privileging life over art in his later plays, Algernon Charles Swinburne explicates each period of Shakespeare's development in a book-length study, Walt Whitman argues that Shakespeare's historical plays represent the seeds of modern democracy, and Washington Irving speculates on the influence of an ill-fated voyage to Virginia on The Tempest.
Mark Twain challenges Shakespeare's identity in his controversial work, Is Shakespeare Dead? His interest in the "Shakespeare question," first sparked by his reading of Delia Bacon's The Philosophy of the Plays of Shakspere Unfolded (Boston, 1857), was reignited in 1908 when he read The Shakespeare Problem Restated (London, 1908) by the British MP Sir George Greenwood. Twain was intrigued by Greenwood's argument that, while there is no evidence that Shakespeare the actor had any familiarity with the law, the author of the plays must have been a lawyer. In fact, Twain was so taken by Greenwood's theory that he lifted, word for word, Greenwood's chapter on "Shakespeare as a lawyer" directly into his own book Is Shakespeare Dead?, without citing Greenwood's name as his source.
Despite the fact that Twain included the title of Greenwood's book in a footnote on the first page of the chapter and set the chapter in smaller type, Greenwood's London publishers accused Twain of copyright violation and prevented Twain's book from being imported to England until the attribution problem was corrected. The dispute between Greenwood's and Twain's publishers was carried out in the New York Times. This manuscript copy of Is Shakespeare Dead?, written in Twain's hand, is dated less than two months before it was published by Harper and Brothers.