Most Americans would agree that academic freedom is a sacred right of the academy and crucial to the American experiment in democracy. But what is it really?

That's the question raised by the Associated Press's July 16 release of emails between Mitch Daniels, when he was the governor of Indiana, and his staff concerning Howard Zinn's "A People's History of the United States." The emails were written in 2010 and Mr. Daniels, whose second term as governor ended this January, is now president of Purdue University in...