In his 34 years on the Supreme Court, Justice John Paul Stevens has evolved from idiosyncratic dissenter to influential elder, able to assemble majorities on issues such as war powers and property rights. Now, the court's senior justice could be gaining ground on a case that dates back 400 years: the authorship of Shakespeare's plays.

Justice Stevens, who dropped out of graduate study in English to join the Navy in 1941, is an Oxfordian -- that is, he believes the works ascribed to William Shakespeare actually were written...