Overheard: choosing a library book

It is always interesting listening to students in the stacks looking for books. Sometimes there are incoherent muttering because the book has been mis-shelved. Often there charming expletives when the book is in the catalog, but the patron did not check to see if it was available (or on reserves). More often than not students bring a friend and it's a tag team event with accompanying diatribe (often increasingly vocal) about a professor sending them on an impossible mission. Leaving my office on the way to lunch this afternoon I heard an interesting theory on choosing a book, I believe it was on the topic of philosophy.

Student one: "I need to pick one, it probably should be old."
Reply from student two: "Just grab it off the shelf, if it smells bad it's old enough."