These 2 characters are opposed in the novel. Ralph arouses our sympathy, and Jack makes us to fell disgusting. If we’d like to watch these 2 characters just as two boys (not as symbols of some political trends), we’ll see that Ralph’s character is shown in development. In the 1st lines of novel he is just a child, appreciating his freedom, carefree and glad about the absence of any adults. Than we can see how he becomes aware that how hard and difficult is it to be the chief, the elder; we can listen his thoughts in which he looks for the reason of all their troubles, of their incapacity to act in coordination. He understands with pain that his intellect and his experience are not enough to answer all that questions, that he’s unable to make other boys willing to keep the fire.
We see that as far as Ralph is growing up he changes his attitude to Piggy: his former arrogance ceases and gives way to respect and he begins to meet Piggy’s advices with interest and gratitude not with irritation. The most important point of Ralph’s growing up is his reaction on the death of Simon. Ralph is probably the only who has enough courage to confess that he himself is responsible for that death. And all further hardships: the betrayal of all the boys, the death of Piggy, being an outcast and, finally, hunting for him – he meets with courage and dignity of an adult man. And is sound very naturally when in the final the officer asks: who is the chief? It’s Ralph who says: me, because he is the only who feels responsible for all that happened, he is the only boy who grew up.
And speaking about Jack I must notice that there is no situation in which we can hear his inner speech. We can see only his acting and we can fell that his only aim from the very beginning is to achieve power, to be the chief. So if Ralph’s character is given in development, Jack is shown on his way to power. When he fails on the elections, he manages to attract the other boy’s attention with hunting: it’s interesting, it has a concrete result, and keeping the fire is dull. So he attracts most of the boys. The other important point is the invention of the mask. Everybody feels that a boy with painted face is somebody other, so he can do everything – and it is not he who does it, it’s a mask.
Finally we see how Jack achieves the complete control about everybody (except Ralph) and the total power, and he is drunk (?) with that power. He consciously orders to kill Ralph but his power of chief ends suddenly at the moment when the children see the adults. It’s a paradox but he’s not eager to say that he’s a chief, so we see that he became a tyrant, he became a murderer, but he didn’t became a grown-up.