"Listen, if there's one sure-fire rule that I have learned in this business, it's that I don't know anything about human nature"

In this quote, Francis Ford Coppola is acknowledging his lack of understanding when it comes to humanity. He is specifying that in spite of remaining in business for a very long time, there is no guarantee that he has a total understanding of how individuals believe and behave. This could be analyzed as a simple admission of his own limitations and a tip to always approach scenarios with an open mind. It also highlights the intricacy of humanity and the fact that it can not be fully understood or anticipated. Overall, this quote acts as a pointer to continuously find out and adjust in an ever-changing world.