Arthur Mitchell is a proper noun and a name that is unique to the individual. However, there are several ways in which the name could be referred to. One could use the first name, Arthur, or the last name, Mitchell, to mention him. Additionally, if one is referring to him in a formal setting, they could call him Mr. Mitchell. In a more familiar context, a close friend or loved one could address him as Art, or Uncle Art if he is an older relative. Finally, in a professional or academic setting, he might be referred to as Dr. Mitchell if he holds a doctorate degree.