The Power of One
One of the central themes in Star Wars is the idea that one person in the right place at the right time doing the right thing can bring down an entire system. The explosion of the Death Star is a collective undertaking, but ultimately comes down to just one person—Luke Skywalker—hitting the bullseye. The film examines the ways that heroes make a difference, by stepping up and doing something hard and sacrificing for the sake of a common goal.
The Force
A guiding principle in the film is the Jedi belief in the Force, a powerful energy field that presides over all things. Both the benevolent Obi-Wan Kenobi and the evil Darth Vader believe in the force, but they use it to achieve different ends. Many people in the world of the film believe that the Force is nonsense, that it is just a made-up magical belief system, but we see that the Force is a guiding principle that does in fact have concrete effects in the world. It is both what allows Darth Vader to strangle a man without touching him and what allows Obi-Wan to throw stormtroopers off his trail. It is both an intuitive sense of one's own power as well as a concrete harnessing of the energy in the world.
Bravery
One quality that all the central characters share is bravery. Luke Skywalker, Han Solo, and Princess Leia all stick their necks out and take risks when it counts the most. Luke goes from being an under-stimulated farmhand on Tatooine to being an integral—if not the most important—participant in the resistance. Han Solo might be a self-serving and sarcastic smuggler who rarely does anything on behalf of the common good, but he is a brave pilot who eventually sees the light and works for the rebellion. Princess Leia is no damsel-in-distress, but an empowered participant in her own rescue, often stepping in to help with the escape from the Death Star and serving as a prominent leader in the Rebellion.
Adventure
The film is, at its core, an adventure narrative, one in which ordinary people, such as Luke Skywalker and Han Solo, are brought into a high-stakes adventure and must make definitive decisions to preserve their own safety and the safety of their companions. Before he meets up with the two droids, Luke Skywalker leads an ordinary life, working on his uncle's farm and hoping to one day become a pilot. While Han Solo has a somewhat more exciting life as a pilot and a smuggler, he does not concern himself with the rebellion. Through their accidental coming together, these characters become embroiled in a suspenseful mission the likes of which they have never experienced before.
Hope
After Obi-Wan Kenobi is slain by Darth Vader, Luke is beside himself with grief, and feels completely unmoored by the loss of his mentor. He grieves the death, but slowly musters the courage to keep going, and even receives some encouragement from an ethereal disembodied voice—that of the now-deceased Obi-Wan. When Obi-Wan fights with Darth Vader before his death, he warns that if Vader strikes him down, he will only become more powerful. This proves to be true, when he continues to speak to Luke and motivate him even after death. It is this spiritual guidance that gives Luke hope and keeps him going.
Good vs. Evil
The Rebel forces are fighting the Imperial forces in what shakes out to be a rather straightforward struggle between good and evil. Darth Vader and the Imperial forces are an evil organization, favoring blunt force, power, and fascistic control over democratic ideals or humanism. The Rebel forces, on the other hand, are committed to giving the galaxy back to the people, and of toppling a political system that holds up a supreme authority above the collective. Furthermore, Obi-Wan Kenobi urges Luke to use the Force for good, warning that Darth Vader uses the Force for evil. Thus, we see that the central conflict in the film is this tension between good and evil, between right and wrong.
Growing up
Luke Skywalker starts the film as a naive teenager, dreaming of bigger and better things and living in the care of his aunt and uncle on a farm on Tatooine. When he gets pulled into the plot to deliver R2-D2 to the Rebels, he begins to have to take on more responsibility and mature as a person. He goes from a post-adolescent to a full-grown adult over the course of the movie, adopting more responsibility and accepting the hero's journey that has presented itself to him.
