The evidence comes from studies of each author’s linguistic idiosyncrasies and how they crop up in Henry VIII. For example, Fletcher often writes ye instead of you, and ’em instead of them. He also tended to add the word sir or still or next to a standard pentameter line to create an extra sixth syllable.
These characteristics allowed Spedding and other analysts to suggest that Fletcher must have been involved. But exactly how the play was divided is highly disputed. And other critics have suggested that another English dramatist, Philip Massinger, was actually Shakespeare’s coauthor.
Which is why analysts and historians would dearly love to determine, once and for all, who wrote which parts of Henry VIII.
Enter Petr Plecháč at the Czech Academy of Sciences in Prague, who says he has solved the problem using machine learning to identify the authorship of more or less every line of the play. “Our results highly support the canonical division of the play between William Shakespeare and John Fletcher proposed by James Spedding,” says Plecháč.