What qualities (negative and positive) does Piggy bring on the boys's lives on the island in Lord of the Flies?
Piggy seems to be quite a unique character in the novel: he seems to be the only true voice of reason, yet he is often incapable of physical work, shows little leadership skills, and is pretty naive as well.
For his positive qualities, he is the one who voices what should be done on the island to maintain order and maximize their chance of rescue: he suggests moving the signal fire, is loyal to the concept of the conch, etc. He also proves to be a loyal and true friend to Ralph.
Despite his positive qualities, Piggy is not taken seriously and often teased due to his physical appearance and health - even Ralph teases him at times. Piggy might have the best ideas, but he lacks the ability to lead the others and seems rather immature when it comes to social and coping skills. Finally, Piggy seems to be rather naive - he truly believes that Jack attacked his and Ralph's camp simply to get the conch, then confronts Jack for not obeying the rules of it.
One of Piggy's qualities that has a positive effect on the boys is his tendency toward rational and organized thought. It is he who advises Ralph about the best ways to create order on the island and improve everyone's chances for survival and rescue. He points out the value of using the conch in meetings to make sure that everyone who has something to say is heard by the others.
A quality that Piggy possesses that causes negativity is his tendency to be a worrywart; he is one of the few on the island who never fully embraces the freedom the boys have from adult authority. His asthma makes him cautious, and this physical frailty, along with his extra weight and poor eyesight, make him a convenient target for bullying. Though it is unintentional, Piggy's weaknesses bring out the worst in boys like Jack, Maurice, and Roger.