When Simon first appears in Lord of the Flies, he is not named but simply described as the choirboy who faints and, according to Jack, is always fainting. When he regains consciousness, he is described as follows:
Now that the pallor of his faint was over, he was a skinny, vivid little boy, with a glance coming up from under a hut of straight hair that hung down, black and coarse.
Another, somewhat fuller physical description occurs later in the book, when the boys have begun to adapt themselves to life on the island:
He was a small, skinny boy, his chin pointed, and his eyes so bright they had deceived Ralph into thinking him delightfully gay and wicked. The coarse mop of black hair was long and swung down, almost concealing a low, broad forehead. He wore the remains of shorts and his feet were bare like Jack’s. Always darkish in color, Simon was burned by the sun to a deep tan that glistened with sweat.
Simon is always described as physically slight and small. He is so short that, when he, Ralph and Jack are walking together, Ralph observes that if Simon goes in the middle, he and Jack will be able to talk over Simon’s head. In character, Simon is thoughtful and reserved, the most sensitive of the boys, though he has the courage to speak out when necessary:
Simon felt a perilous necessity to speak; but to speak in assembly was a terrible thing to him.
“Maybe,” he said hesitantly, “maybe there is a beast.”
The assembly cried out savagely and Ralph stood up in amazement.
“You, Simon? You believe in this?”
“I don’t know,” said Simon. His heartbeats were choking him.
It is Simon’s sensitive, emotional nature that leads him to believe that there might be a beast, and later to fall under the spell of the Lord of the Flies, which his rational mind knows is only a pig’s head on a stick. Golding describes his struggle to preserve his sanity:
Simon’s head was tilted slightly up. His eyes could not break away and the Lord of the Flies hung in space before him.
“What are you doing out here all alone? Aren’t you afraid of me?”
“There isn’t anyone to help you. Only me. And I’m the Beast.”
Simon’s mouth labored, brought forth audible words.
“Pig’s head on a stick.”
“Fancy thinking the Beast was something you could hunt and kill!” said the head. For a moment or two the forest and all the other dimly appreciated places echoed with the parody of laughter. “You knew, didn’t you? I’m part of you? Close, close, close! I’m the reason why it’s no go? Why things are what they are?”
Given Simon’s mystical nature, it is ironic that he is killed while attempting to communicate a simple, mundane fact about the nature of the beast: that all the while the boys have been afraid of a paratrooper’s dead body. His death symbolizes the extinction of goodness and innocence on the island.