Came to this through the index thread.
"Lucas: Well, he is a teacher, not a real Jedi. Understand that?
Kasdan: I understand what you’re saying, but I can’t believe it; I am in shock."
THis made me laugh for some reason
As I see it, the idea was that Yoda and Palpatine are “masters” while Vader and Obi-Wan are “knights”. “Knights” use lightsabers and tend to join the action while “masters” prefer giving orders and don’t need lightsabers because they can use The Force itself.