From the start, the novel shows the thread of irrationality that motivates group behavior. Piggy would be, rationally speaking, the best choice as leader, because he is the most intelligent—but he also has odd speech patterns and lacks charisma. Jack is a natural leader and asserts, for such irrational reasons as his ability to sing, that he should be in charge:
“I ought to be chief,” said Jack with simple arrogance, “because I’m chapter chorister and head boy. I can sing C sharp.”
The boys, however, choose Ralph, because he most fully looks like a person of authority. He has an air of stillness or calm, he is tall, he is more attractive than Jack, and he has possession of the conch, which sits on his lap. This symbol of authority, repeatedly described as "delicate" (symbolizing the fragility of civilization) lends Ralph gravitas in the eyes of the other boys:
there was a stillness about Ralph as he sat that marked him out: there was his size, and attractive appearance; and most obscurely, yet most powerfully, there was the conch.
Leadership in this novel, however, changes, and the battle between the rational form of authority represented by Piggy and Ralph and the irrational return to the id represented by Jack is a fraught one. Piggy and Ralph retain the self discipline to defer gratifying immediate desires. Instead, they concentrate on the future, which centers on tending the fire. This, they hope, will be the means of getting rescued. The other boys, however, move toward barbarism and Jack, willing to sacrifice the future to the present moment (though, ironically, their burning down of the jungle brings rescue).