Let’s begin by understanding the changes that copyright law has undergone. There are five dimensions. First, duration: Disney builds its empire on top of the public domain because the culture in the public domain was free to take. It was free to take because copyrights expire, and when they expire, the work passes into a public domain. What is the public domain? The public domain is a lawyer-free zone. It is a place where culture lives permission-free. One needs no authority from anybody to take and build upon culture that lives in the public domain. It is guaranteed by the freedom of the public domain forever. Copyrights expire because the Constitution says they are to be limited.