The Last Jedi may have its haters, but there's no denying that the movie adds an awful lot to the mythology of the franchise. If there's one and only one thing that director Rian Johnson did well in this movie (and there's more than one thing), it's that. Specifically, he explored more of what can be done with The Force and, even more specifically, what a Force ghost can do.
Warning: spoilers ahead for Star Wars: The Last Jedi. During a very pivotal scene in the movie, we see Luke getting ready to burn down the Force tree on Ahch-To. At this point, his old master Yoda comes to guide him as a Force ghost. Instead of Luke burning down the tree, Yoda calls down a bolt of lightning and does so himself. We've never seen Force ghosts do anything more than talk to the living in a Star Wars movie before, so that was a pretty significant moment. Here's what Rian Johnson had to say about it in a recent interview.
"The truth is, because 'Star Wars' until 'The Force Awakens' has been set in amber and we hadn't had a new 'Star Wars' movie in 10 years, you forget that they were introducing new Force stuff with each movie, based on the requirements of the story. Force-grabbing didn't come around until 'Empire,' it wasn't in 'A New Hope.' Same with Force ghosts. They'd introduce new ideas of what could happen with the Force each time...The one point where we do introduce a bit of a twist in terms of Force ghosts is where Yoda calls down the lightning onto the tree. That, I think, is a tantalizing hint of the potential of someone who is a Force ghost interacting with the real world."
It's sometimes easy to forget as Star Wars fans that this knowledge of what The Force can do didn't all come at once. The franchise has become so ubiquitous that we may forget that the things we know about The Force were revealed over the course of the entire saga. Rian Johnson has certainly furthered that in Star Wars: The Last Jedi. One thing we still haven't seen is a Dark Side Force user returning as a Force ghost. So, what does Johnson think of that possibility?
"I think that would be interesting. We haven't seen them in the movies as far as I can remember. But that would be really interesting considering the dark side is about self-preservation, trying to find immortality, and the notion that the light side actually got to it through selflessness, what would the dark side version of that look like? There's so much cool [stuff] to think about if you're willing to open your head a little bit!"
Rian Johnson is likely going to be showing us a lot more about The Force, as he's been tapped by Disney and Lucasfilm to develop an entirely new Star Wars trilogy, set apart from the Skywalker saga. If we hope to see anything more, like maybe a Dark Side Force ghost, in this trilogy, it's up to J.J. Abrams on Star Wars 9. For more with Rian Johnson, you can check out the full interview with the L.A. Times