What does The One and Only Ivan prove about art?

Throughout The One and Only Ivan, artistic expression is a dominant theme. From his infancy in the wild, Ivan gained the name Mud because of how he would paint on his mother's back using mud. While being raised in Mack and Helen's house, Ivan used cake frosting to paint on the refrigerator door. Later Julia slipped Ivan paper and crayons so that Ivan could draw while in his cage. When asked by Ruby, Ivan is forced to confront the question of why he makes art; he realizes that he makes art because it makes him feel quiet inside. What he doesn't understand is that he gravitates to art because it acts as a form of expression and freedom in a life that is otherwise severely limited. Ultimately, it is artistic expression that enables Ivan to communicate his desire to see Ruby taken to live a better life in a zoo.