Tom Stoppard, whose death at age 88 was announced on Saturday, may or may not have been the greatest playwright of the past half century or so, but he was undoubtedly the most intellectually daring, historically inquisitive and encyclopedically knowledgeable. If you throw in the rhetorical brilliance, the heart and the boundless wit that coursed through his greatest works, his pre-eminence is hard to challenge. Across his career he collected five Tony Awards for best play (a record) and an Oscar for the screenplay for “Shakespeare in Love”—probably the work that brought him the largest audience. PREMIUM British dramatist Tom Stoppard circa 2013. The theater’s importance as a locus of intelligent inquiry and intellectual ferment—not momentous, alas—owes a great debt to his influence. Mr. Stoppard insisted, through his works, that theater could and should engage with ideas, with philosophy, with the vast knowledge amassed by writers and thinkers of many ages. And he brought his multifarious interests to sometimes bewildered but almost always fascinated audiences with an assiduousness that remains incomparable—and amusing. Theatergoers of today …