If Americans are “deeply religious people,” what does religious studies scholar, Stephen Prothero, mean when he claims that many Americans are also “religious illiterates”?

If Americans are “deeply religious people,” what does religious studies scholar, Stephen Prothero, mean when he claims that many Americans are also “religious illiterates”?

Book for course is World RELG4 Introduction to World Religions
Robert E. Van Voorst, 2020
Cengage