Piggy is the voice of reason and the scientific mind in the novel Lord of the Flies. He is fat, wears glasses, and has asthma. As a result, he is only a voice, an educated, common sense voice, but he cannot back his ideas with action. He is not a man of action. Therefore, over time he becomes a subject of ridicule and mistreatment. However, he does manage to make an impression in some respects on the boys.
First, it is Piggy's glasses that enable the boys to build a fire. Without them, without Piggy, this would not have been possible, and the boys would have had little hope of rescue and certainly would not have been able to cook food, namely meat.
Secondly, it is Piggy's idea to make the conch an important part of the group's gatherings/meetings. The conch gives the right to speak to the boy who holds it. Without it, Piggy's voice would never have been heard. But his "power", his voice of reason, his scientific logical ideas are voiced and heard. He is definitely an idea man, a thinker, the person who can hypothesize ways to solve problems, but he does not have the physical strength to back up his ideas. He becomes a scapegoat, that part of society that people cannot or will not recognize as important and vital because he is not physically imposing.
Last of all, it is Piggy's idea to move the fire to a more conspicuous location, hoping to increase the chances of rescue. He is the one who realizes that the beast does not exist, but is actually part of the boys themselves. His logic, his insight, his ideas, his concern all go unnoticed as far as their importance to the group because he is not physically imposing and cannot even act upon his own ideas.