From “Revenge of the Jedi” Story Conference Transcript, July 13 to July 17, 1981 with series creator George Lucas and writer Lawrence Kasdan.
Kasdan: The Force was available to anyone who could hook into it?
Lucas: Yes, everybody can do it.
Kasdan: Not just the Jedi?
Lucas: It’s just the Jedi who take the time to do it.
Marquand: They use it as a technique.
Lucas: Like yoga. If you want to take the time to do it, you can do it; but the ones that really want to do it are the ones who are into that kind of thing.