He has physical disadvantages because he is fat and asthmatic and is short sighted. Without his glasses, everything becomes a blur.
He is very intelligent - in Chapter 1 it is his idea to make a list of names, and it is he who realises that no adult knows the boys are on the island. Later he suggests making a sundial and hats. "What intelligence had been shown was traceable to Piggy." Ralph recognises Piggy could think: "Piggy, for all his ludicrous body, had brains."
However, he does not speak as grammatically accurately as the others:" How can you expect to be rescued if you don't put first things first and act proper". Perhaps this is to suggest he wasn't as well educated as the others and that he is not from the right class of people to be a successful leader. At the time the novel was written most power was still in the hands of the middle and upper classes. "Piggy was an outsider, not only by accent, which did not matter, but by fat, and ass-mar, and specs, and a certain disinclination to manual labour."
He is embarrassed by his nickname, and he behaves with dignity when Ralph betrays the name to the others. We never know his real name.
He is kind and considerate to the littluns. He helps the boy with the birthmark talk about the 'snake-thing' and helps Percival talk about the beast. He is later often left to care for them when the others are exploring and hunting.
He has the most mature attitude of any boy on the island. He scornfully sees the other boys "Acting like a crowd of kids".
He is pragmatic. When Simon dies, Piggy tries to convince Ralph there was nothing they could have done: "It was an accident... and that's that".
Like Ralph, he believes in civilised values and clings to what creates order: " I just take the conch to say this. I can't see no more and I got to get my glasses back". When they go to the fort to confront Jack, he shouts "I got the conch!" to try to show Jack that he has a right to be heard.
Piggy and the conch are destroyed together by the rock Roger levers. Thus both intelligence and the symbol of authority are dead, so we know that there is nothing left to stop Jack gaining full control.
At the end, Ralph mourns the fall through the air of "the true, wise friend called Piggy".
The first time we meet Simon, he is in his choir robes. He faints on the beach because of the heat and Jack mocks him. We know he is delicate. He has epilepsy.
He is "a skinny, vivid little boy, with a glance coming up from under a hut of straight hair that hung down, black and course". His hair hides his face, which hints to us he is secretive.
He is imaginative: he sees the buds on the bushes as "Like candles. Candle bushes. Candle buds".
He is helpful and works for the good of others; he is the only one to stick with Ralph to make the shelters. He is kind to the littluns and finds fruit for them.
The others recognise he is 'different' to them in some way. Ralph says "He's queer. He's funny." Piggy says "He's cracked".
He has "a secret place in a clearing full of flowers and butterflies", and is sufficiently at one with the jungle to walk in it alone at night. He is at one with nature and he has no fear. "He walked with an accustomed tread through the fruit trees."
He seems able to prophesy - he is the first to suggest that "it wasn't a good island" and he tells Ralph, "You'll get back to where you came from".
He is the most perceptive about the beast. He says "maybe there is a beast... What I mean is... maybe it's only us". He is the only one to see that the problems on the island stem from the boys' relationships with each other, not from an outside force. Yet nobody understands what he's trying to say.
When the Lord of the Flies 'speaks' to him this idea is reiterated: the voice in Simon's head says "Fancy thinking the Beast was something you could hunt and kill!... You knew, didn't you? I'm part of you?"
He is killed just as he is about to reveal the truth. It is ironic that he is the only one who finds out that the 'beast' was a dead parachutist, but is denied passing on the message because the group of boys think, in their frenzy, he is the beast.
Simon's close relationship with nature seems to carry on even after he is dead: " The waves turned the corpse gently in the water. ... Softly, surrounded by a fringe of bright inquisitive creatures, itself a silver shape beneath the steadfast constellations, Simon's dead body moved out towards the open sea".
Jack is the leader of the choir. He was the chapter chorister, can sing C sharp, and was the head boy at school.
He has red hair and is tall, thin and bony. "His face was crumpled and freckled, and ugly without silliness". His fiery hair and his ugly appearance give us clues to his hot-headed, unpleasant character. "Out of this face stared two blue eyes, frustrated now, and turning, or ready to turn to anger."
He is proud and arrogant.
He is hungry for power. When we first meet him he bosses the choir around; later he undermines Ralph's leadership and sets up his own tribe against Ralph, even though he loses a vote. He gradually becomes a dictator. When he orders the tribe to tie up Samneric her boasts to Ralph "See? They do what I want."
He knows as soon as Ralph asks him that the choir should be hunters. Hunting then pre-occupies him more and more through the novel.
He can't kill the first pig he sees because of "the enormity of the knife descending and cutting into living flesh; because of the unbearable blood". Yet he quickly puts aside any doubts.
Jack thinks of nothing but hunting. "All you can talk about is pig, pig, pig!" Ralph says angrily.
Jack paints on a mask to help him hunt better. The paint gives him a liberation into savagery: he is able to do savage things now he looks more like a savage.
He is so moved by having killed a pig that he isn't anxious about the ship that went by while the fire was out. All he thinks about is the knowledge that "they had outwitted a living thing, imposed their will on it, taken away its life".
By the end, Jack has moved on even further. His prey has gone beyond pigs - he is keen to hunt Ralph.
He commits the first act of violence towards another boy on the island when he thumps Piggy. "His voice was vicious". He gets gradually more violent towards other boys: he has no thought for Piggy when he steals his glasses and later he ties up and beats Wilfred.
He pretends not to be frightened of the beast - but is shivering and croaking when he sees the 'beast' on the mountain. Does this suggest that he's not really as brave as he'd like to think he is?
Although Jack says near the start: "We're not savages", it's soon clear he doesn't care about the rules or being civilised: "Bollocks to the rules! We're strong - we hunt!" He rejects the order that had been established on the island: "We don't need the conch any more".
At the end, he has no remorse for Piggy's death. He declares himself Chief. He has lost the name Jack, which suggests he has lost all.