Which criterion would Adler rate as essential for book inclusion?

• A. The book is entertaining
• B. The book is inexhaustible
• C. The author is living
• D. The book is a biography

Answer: (B)

The key idea here is that a book should offer enduring usefulness. An inexhaustible work provides ideas and insights that keep yielding new understanding no matter how often you revisit it or in what context you encounter it. This kind of lasting, adaptable value is what Adler would look for to merit inclusion, because the book remains relevant across time, disciplines, and questions.

Entertainment alone can be enjoyable but doesn’t guarantee lasting impact. Whether the author is living doesn’t determine a book’s ongoing value—a work by a deceased author can still be profoundly important. A biography is a genre choice and doesn’t address whether the book’s content can be repeatedly explored in meaningful ways. So the most fitting criterion is inexhaustible content.