Some other fantasy lands might have room for cowardly lions, but not Narnia. Prince Caspian defines its characters by the courage they possess. Whether they stand up or sit down, these heroes will fight, fight, fight. Even the heroes who don't wield a blade display courage—remember Lucy's courage to believe she saw Aslan when none of the others did? The villains are also defined by their courage, or rather, lack thereof. Miraz is a warrior, but he confuses courage with the willingness to fight. And the lords Glozelle and Sopespian stab a guy in the back, so 'nuff said, right? Point is: every character has some type of relationship with the ideal of courage, making it a super-ultra-mega important theme.
Courage is not about what the characters do in Prince Caspian. It's about why they do it.
No one is taught courage in Prince Caspian. You either are or you aren't.
Back in the days of knights, dragons, damsels, and stone towers, chivalry and courage went hand-in-hand. Chivalry was the code the knight lived his life by, and it included such virtues as honor, gallantry, courtesy, generosity, valor, and even love. The knight who lived by chivalric conduct was considered a true knight. Today, chivalry isn't too much in fashion—possibly because knighting isn't as chic as it used to be. But in Prince Caspian, chivalry makes a modern-day comeback with heroes like Peter and Caspian suggesting that the best of the chivalric code can be of use today. Sure, we might not call it chivalry—principles seems more up-to-date. Slice how you'd like, it's in the book all the same.
The principles of Prince Caspian come directly out of classical romance stories (by which we mean true romance and not lovey-dovey romance).
Although he's the protagonist, Prince Caspian's principles are molded more by the people around him than by any of his own decisions.
Prince Caspian's take on the coming of age theme is totally odd. At first glance, the novel seems to promote a Geoffrey the Giraffe philosophy—i.e. "I don't wanna grow up; I'm a Toys"R"Us kid." Characters like Peter, Trumpkin, and Susan—especially Susan—are criticized for their more grown-up traits, and at the end, Peter and Susan are flat out told they can't return to Narnia because they're too old.
On the other hand, Prince Caspian also requires its characters to be exceptionally adult in many situations. They have to fight in wars, butcher a bear for survival, and Peter even uses politics to his advantage in the fight against Miraz. And let's not forget the killing. In a "having your cake and eating it too" maneuver, the novel suggests we need to stay children and grow up at the same time.
C.S. Lewis once said, "When I became a man I put away childish things, including the fear of childishness and the desire to be very grown up" (source). It's what we think he had in mind when conceiving of Prince Caspian's coming of age theme.
Some characters who are already full grown, such as Trumpkin, come of age during the course of the story.
The good vs. evil split is pretty straightforward in Prince Caspian. In the blue corner, wearing lion gold, consisting of our main characters, are the good guys. In the red corner, wearing Telmarine green, consisting of some devious fellows indeed, are the bad guys. And then they fight.
Yep, there's not much subtlety in the way the novel handles issues of good and evil. The good guys are good, the bad guys are villainous, and the middle ground is narrow. It's pretty simple by modern standards, but that also might be the point. Prince Caspian borrows many themes from classical works—we're looking at you, chivalry—and it doesn't get more classic than a simple tale of good versus evil.
Prince Caspian, and the Narnia series as a whole, uses simplistic notions of good and evil because it's a children's story. As a result, they totally underestimate what children can and can't accept in their stories.
Miraz is certainly our antagonist, but other characters are much eviler. Think Nikabrik. In the same way, Caspian is our protagonist, but characters like Peter represent the "good guy" better.
War! What is it good for? Absolutely depends on whom you ask. Scholar Michael Ward reads Prince Caspian as a story centered on war and martial law. It's all about the need to fight rather than "allowing aggressors to have their way." To balance this, he argues that Lewis included chivalry to "[impose] restraints on the practice of war so as to avoid unnecessary (that is cruel) violence" (source). Then again, David Holbrook reads a novel where "the trouble is that excited delight in violence is combined with a tone of endorsing it as all jolly good fun, and then endorsed by [a] solemn didactic message, urging that this is the way to the Kingdom of Heaven" (source). Ultimately, we'll say this: war is undeniably an important theme in Prince Caspian, but whether or not that's a positive thing will depend on the reader.
Caspian's war with the Telmarines is an example of a holy war. Its main goal is to change the religious standard of Narnia.
Alternatively, we could look at Caspian's camp as a group of environmental terrorists done Narnia-style.
Nostalgia is a lot like viewing the past through rose-tinted glasses. In which case, Lewis's writing glasses must have been rose-tinted because Prince Caspian doesn't just envy the past through nostalgia—it straight-up worships it. Everything about Old Narnia is seen as a type of golden age for Caspian and his people, and their entire war is an attempt to make Narnia more like the Narnia of the past. They even receive help from the Pevensie children (ye kings and queens of yore). The characters who don't desire this past or who desire a different type of past are written as ignorant at best, or more commonly, as villains.
Even if he doesn't realize it, Miraz honors the past by his acknowledgment of Peter's legal power to challenge him to a duel.
The use of elements of our own world's past, such as the gods and creatures of Greek myth, helps connect the importance of the past in Narnia to the importance of the past in our world.
There's no place like home. True if you live in Kansas; true if you live in a place where the trees come to life and badgers talk. Like the golden era from "Memory and the Past," Prince Caspian is all about reclaiming the idyllic home. The Telmarines have turned Narnia into a place incompatible for the Old Narnians, and the civil war is all about undoing that process so the Old Narnians can call their home, well, home. It's the ultimate extreme home makeover—only they have to tear down and rebuild an entire kingdom.
After Caspian flees from Miraz's castle, his story becomes one of rediscovering and preserving his new home.
The Pevensie children can't stay in Narnia like in The Lion because it's not their home anymore.
Probably no surprise to see religion rearing its head in Prince Caspian, is it? C.S. Lewis's conversion to Christianity is one of the more famous instances in an already famous author's biography, and his Christian apologetics like Mere Christianity are pretty famous themselves (not Narnia famous but still). So it makes sense that Prince Caspian contains many parallels to the Christian religion. Aslan represents Jesus Christ, Peter and Caspian represent knights in the European Christian tradition, and Lucy's struggle with faith is a quintessential Christian struggle. For some, including J.R.R. Tolkien, this amount of allegory will be a little too much. For others, it'll be just right.
The Telmarines aren't given a religion of their own, making it difficult to read the war as a conflict of religious interests.
Peter and Susan's exclusion from Narnia definitely has religious undertones—especially given Susan's controversial fate at the end of The Last Battle.