William Golding represents many concepts through the characters within Lord of the Flies. Each character and their subsequent actions are crafted very deliberately in order to build a representation that extends far beyond the boys on the island. Both Piggy and Ralph are important to the symbolism created in the book, and Piggy's relationship with Ralph throughout their time on the island is directly responsible for Ralph's evolution in the novel.
In the initial chapters of the novel, Piggy possesses far more kindness than Ralph does. The examples of this are in the first two chapters. As the group of boys first assembles, Piggy takes time to try and learn who each of the boys are, including the group of boys known as the littluns, who are largely forgotten and ignored by the older boys. When the older boys want to run off and explore, it is Piggy who stays behind to keep an eye on the littluns. Conversely, Ralph is cruel in the beginning. He tries to keep Piggy at arms length, and even shares his nickname in order to get a good laugh.
Piggy is also more articulate than Ralph, especially as the novel progresses. The more chaotic the novel becomes, the more difficult it is for Ralph to convey his ideas. After the "attack" by Jack's tribe in Chapter 11, Ralph becomes confused, and cannot clearly get his point across as they are discussing what needs to be said to Jack. It becomes noticeable enough that it even begins to change Sam and Eric's opinion of Ralph. Even while this happens, Piggy, ever loyal to Ralph, gently prods him in order to remind him of his point. Piggy never waivers in what is needed, and guides Ralph back to their purpose when he starts to stray.
Piggy is also more steadfast than Ralph. From a symbolic perspective, Piggy is meant to represent intellect and reason throughout the novel. These are concepts that require a great deal of understanding and mental strength, which are represented in Piggy's unwavering actions. No matter what happens, Piggy stands behind the idea of Ralph as the leader, and the power of the conch and the rules associated with it. Ralph, on the other hand, is not as able to stand strong on his ideals. He questions his choices and is more easily swayed by the actions of the other boys, such as when he goes hunting with Jack's tribe. Ralph is representative of the everyman, and therefore he must struggle in places where Piggy can stand strong, just as many readers may struggle with the decisions they are faced with each day.