There are several. The theme of narrow-mindedness is one. Throughout the novel, many are guilty of being short-sighted. The narrator complains of the grown-ups not being able to interpret his painting.  The adults are often incapable of accepting anything other than what can be immediately seen.The little prince is the symbol of open-mindedness.

One of the notable characteristics of The LittlePrince is that it invites many different meanings and interpretations. One interpretation is that The Little Prince is an allegory about growing up and the importance of retaining a sense of child-like wonder about the world into adulthood. Antoine de Saint-Exupéry suggests that the curiosity and open-mindedness of children are often replaced by an obsession with mundane facts, practicalities, and superficial judgments in adulthood. He explores this idea through characterization, primarily the little prince himself, who symbolizes and embodies the curious spirit of childhood. The little prince asks questions about the world and is constantly learning and growing from his experiences, and he is prepared to learn something from each new encounter. For example, when the little prince sees thousands of roses that are identical to his own he realizes that his own rose is unique and valuable due to the effort and time he has invested in its growth.

The inquisitive nature of the little prince can be contrasted with the adult characters in the text, who come across as narrow-minded and pedantic. This contrast emphasizes the fact that children often lose their open-mindedness as they grow up. For example, the little prince meets a businessman who is obsessed with the stars due to their numerical value, saying "I count them and then count them again." The businessman continues his monotonous pursuit, living a life of boredom as he fails to appreciate the beauty of the stars he is counting. In addition to this character, other adults in the book, such as the vain man, the drunkard, and the geographer, represent the various impoverishments of adulthood. As the narrator states: "I have lived a great deal among grown-ups. I have seen them intimately, close at hand. And that hasn’t much improved my opinion of them." The author suggests that the qualities that the little prince embodies are valuable but are sadly often lost when one transitions into adulthood.

Following this, the author suggests that adults do not ask the right questions when meeting people and instead focus on mundane details. In one of many comparisons made between adults and children in this book, Antoine de Saint-Exupéry suggests that adults are seemingly obsessed with numbers, while children are curious to discover what really drives people:

Grown-ups are very fond of numbers. When you tell them about a new friend, they never ask you the kind of questions that should be asked, such as: “What kind of voice does he have?” “What are his favorite games?” “Does he collect butterflies?” Instead, they ask: “How old is he? How much money does his father earn?” They really do imagine this is the best way to discover what sort of person he is!

Here, the author suggests that somewhere between childhood and adulthood, a person stops being interested in mystery and beauty and instead becomes fixated on mundane practicalities.

Again, this idea is represented when the narrator tells us about a picture he drew when he was a child. Although he intended the drawing to be of a snake digesting an elephant, adults interpreted it in a literal sense, seeing a floppy hat. Here, we see how the adults have lost their sense of imagination and no longer look beneath the surface. Compounding this, the adults even tell the young narrator to give up the idea of being an artist in favor of more practical pursuits like mathematics and geography. This is an illustration of the main lesson in the book, which is that “children quite naturally see with the heart, the essential is clearly visible to them.”

Overall, the lesson of this allegory is to value childhood and the sense of curiosity and enthusiasm that children naturally have: "All grown-ups were once children... but only few of them remember it.” Despite the fact that adults often forget they were once children and are jaded by the harsh realities of the world, the author maintains the importance of remembering one's childhood and one's roots, much as the little prince remembers his home in the story.

The Little Prince has often been read as Christian allegory. In the broadest sense, an allegory is a story with a thinly veiled meaning. More particularly, what literally happens in allegory mirrors or represents something else. Like Christianity, it emphasizes the centrality of love and explores what love is. The Little Prince learns that love is not based on the uniqueness of the beloved. He realizes this when he discovers his rose is not unique in all the universe, as he had believed. Love is, instead, based on the relationship one has with the beloved object. This can be read as Christian allegory. Christianity also emphasizes the relational aspects of love.

The Little Prince himself has been seen as a Christ figure. Like Christ, he looks at the world and entire universe through a different set of lenses than most adults. He dismisses most of what they find important as non-essential. He also is willing to sacrifice himself for the one he loves, the rose. Eventually he allows himself to physically die so that he can return to her. Like Christ, too, he seems to have had a bodily resurrection back to his asteroid, as the pilot can never find the prince's corpse.

There are many lessons of The Little Prince. One of the most important ones is what the fox teaches the little prince: to see with one’s heart and not with one’s eyes. The little prince loves his rose. She is fragile, so he places a protective cover over her to keep her safe. In part, this also teaches the lesson of individuality. When he comes across the rose garden:

he was overcome with sadness. His flower had told him that she was the only one of her kind in all the universe. And here were five thousand of them, all alike, in one single garden!

Although the reader might not be able to discern the prince’s rose from any other similar flower, the prince realizes that he sees her individuality and loves her with all his heart. Even when he thinks that "I thought that I was rich, with a flower that was unique in all the world; and all I had was a common rose," he still realizes that his rose is unique to him.

Still, he leaves her because he must go off and see other worlds. Like the author himself, the little prince must travel from his home and leave his loved one behind. The pain that this causes him is acute, which is another lesson from the story. Love causes great joy and great anguish at times, especially when we must be parted from our loved ones.

Another important lesson is that children see things without the jaded view that adults often have. This is seen in the picture of the boa constrictor that the adults see as a hat. Children are more innocent and retain the vivid imagination and wonder that, unfortunately, adults lose as they get older. Another picture the pilot draws for the prince is only of a box. The little prince is able to see the sheep inside because of his innocent way of viewing the world around him.

As an allegory Le Petit Prince by Antoine Saint-Exupery expresses lessons of friendship and altruism.  Saint-Exupery once wrote, etre homme, etre responsable [to be man is to be responsible], and this expression of man's purpose is the philosophy of Saint-Exupery's The Little Prince. The relationship that the little prince has with his rose on the planet is pivotal to the novel as the prince learns that it is his responsibility to the rose, rather than his love for its beauty. In fact it is this responsiblity that drives him back to the planet and that gives his life meaning.  The prince also learns that altruistic gestures are more rewarding than selfish ones.

In Saint-Exupery's allegory there are unnamed characters who symbolize certain phases of human life.  For instance, the king represents authority, the businessman respresents greed, and the lamplighter respresents devotion to duty. The flower is a flirtatious woman, the serpent is death, the fox represents trickery.  For instance, it is the fox who teaches the prince about the importance of one's responsibility to the loved one.  He explains to the prince that by taming him, the prince has invested himself in the fox, thereby making the fox more special to the prince.  Thus, what one gives to the loved one is more important than what one receives in return.  Because of this lesson, the prince decides to return to his planet where his responsibility, the rose, needs him. 

The links below will connect you to another question and another site on Saint-Exupery's novel which may be of help to you.

Le Petit Prince by Antoine de Saint-Exupery isread as both a child's fantasy tale and as an allegory for adults that reaffirms the importance of friendship, altruism, love, and imagination.  The main theme of an individual's responsibility to another is illustrated in the narrative of the little prince from planet B 612, whom a pilot meets when he crashes in the desert.  The prince has fled the asteroid where he has lived because of the tyrannical love of his only companion, an animate rose.  Before coming to earth, the prince has traveled to six other planets where he has had various experiences.  His narrative of these experiences, while delighting children, also catalogs human weaknesses and failings, thus illustrating Saint-Exupery's themes of altruism and imagination.   For instance, in Chapter IV, the motif of the importance of the imagination is illustrated as the Turkish astronomer discovers asteroid B612, but his discovery is ignored because of his strange clothing.  Years later, when he presents his discovery again, wearing European clothing, it is accepted.  In another example, the three-petaled flower of Chapter XVI, who has spent its life in the desert, assumes that Earth is populated by very few people.  Even in the first chapter, Saint-Exupery depicts children as much more open-minded and creative in their thinking than adults.

To exemplify the theme of altruism, Saint-Exupery portrays the prince learning through his travels that he has a responsibility to the rose, and it is that, rather than any intrinic characteristic of the rose, such as beauty or goodness, that makes her special to him.  So, he returns by having a snake bite him.  For, it is only by spirit that he can make the journey back to his asteroid.

Many themes found in Saint-Exupery's The Little Prince depict many different principles. In fact, it is widely recognized that there isn't one social issue of Saint-Exupery's time that he neglected to touch on in the little book (eNotes, "Social Concerns/Themes"). However, the most dominant theme and also principle explored in the book is that of spiritual understanding. Time and time again, Saint-Exupery teaches that one must look beyond the corporeal world; that true understanding lies in the non-obvious, in the spiritual world that consists of things such as love and faithfulness.

We see the basic principle of spiritual, or true understanding, relayed in the very first chapter. We learn that when the pilot was a boy he drew a picture of a boa constrictor that had just eaten an elephant. He called his picture a drawing of a "boa constrictor from the outside." If you look very closely at the drawing, you'll see that it is barely recognizable as a snake if you'll notice that it has eyes. However, all of the adults he showed it to concluded that it was a drawing of a hat. Saint-Exupery uses this idea of the drawing to teach that there are those in this world, especially adults, who are too materialistic and too lacking in foresight to be able to notice anything beyond surface level. We learn that even as an adult the pilot continued to show his drawing to others and was able to judge whether or not they were capable of reaching "true understanding" by whether or not they saw the picture as a hat (Ch. 1). The ability to see beyond surface level can be likened to the ability to see beyond the corporeal and to understand the spiritual world. The little prince in our story is the only one the pilot ever met who was capable of reaching "true understanding" and seeing beyond the corporeal.

As we get to know the prince further and learn about his adventures, we also see that other basic principles Saint-Exupery touches on in the book are about love, friendship, faithfulness, conceit, drunkenness, laziness, and materialism. Hence, we see that there really are very few principles that Saint-Exupery fails to touch upon in his parable-like story.