10 Star Wars Theories That Make Appalling Sense

During Luke's training in The Empire Strikes Back, Yoda sends Luke into a cave infused with the power of the Dark Side to face his sternest test. There Luke is confronted with a vision of Darth Vader and, inflamed by anger, attacks it with his lightsaber. The vision is revealed to have Luke's own face and upon emerging, Luke is told by Yoda that he has failed. He gave into his hatred, and the Dark Side is too strong within him.

This theory suggests Luke never left the cave. Either he died there, or is comatose in the cave having been stripped of his power by the Force before he turned completely to the Dark Side. The rest of the series after Luke's failure in the cave is what Luke sees in his mind after his failure and possibly death.

This theory helps explain how Luke becomes a Jedi even after Yoda is explicit about Luke's inability to master the Force. Luke lives out a power fantasy that first sees him create a dark surrogate father figure in Darth Vader, and then kill that figure to vanquish Luke's anguish at never knowing his true father.

Luke's fantasy world also helps explain his absence from the galaxy at the start of The Force Awakens - he is trying to escape the galaxy he has made for himself and return to reality. He is trying to wake up.