Piggy is the intellectual with poor eyesight, a weight problem, and asthma. He is the most physically vulnerable of all the boys, despite his greater intelligence. Piggy represents the rational world. By frequently quoting his aunt, he also provides the only female voice.
Piggy's intellect benefits the group only through Ralph; he acts as Ralph's advisor. He cannot be the leader himself because he lacks leadership qualities and has no rapport with the other boys. Piggy also relies too heavily on the power of social convention. He believes that holding the conch gives him the right to be heard. He believes that upholding social conventions get results.
As the brainy representative of civilization, Piggy asserts that "Life . . . is scientific." Ever the pragmatist, Piggy complains, "What good're your doing talking like that?" when Ralph brings up the highly charged issue of Simon's death at their hands. Piggy tries to keep life scientific despite the incident, "searching for a formula" to explain the death. He asserts that the assault on Simon was justifiable because Simon asked for it by inexplicably crawling out of the forest into the ring.
Piggy is so intent on preserving some remnant of civilization on the island that he assumes improbably enough that Jack's raiders have attacked Ralph's group so that they can get the conch when of course they have come for fire. Even up to the moment of his death, Piggy's perspective does not shift in response to the reality of their situation. He can't think as others think or value what they value. Because his eminently intellectual approach to life is modeled on the attitudes and rules of the authoritative adult world, he thinks everyone should share his values and attitudes as a matter of course. Speaking of the deaths of Simon and the littlun with the birthmark, he asks "What's grownups goin' to think?" as if he is not so much mourning the boys' deaths as he is mourning the loss of values, ethics, discipline, and decorum that caused those deaths.