Foreshadowing - Golding uses foreshadowing in this passage to hint to the reader events and ideas that will later come in the novel.  He hints that Ralph and Jack are both characters that possess thoughts of killing living creatures. Even though we are told that Jack is the one with the opportunity to kill the pig, and that it is given that he is the person with the deepest urge to kill, the conversation between Ralph and Jack following the scene tells us that out of the three boys, Jack, Ralph, and Simon, that two of them are interested in killing. Golding hints at the reader that Jack and Ralph will have a hand in taking someone's or something's life later in the novel and that Simon will not. Golding also tells us that the three boys were unable to kill the pig because of the thought of hurting a living being and spilling blood is too much to handle for the boys and this symbolizes how their good morals and high standards have affected the boys' thought processes. It shows their behaviors and close ties to civilization at the current stage in the book; but that soon could change. This is because Golding tells the reader that Jack gives his word, that next time a creature's life is at his mercy, he will kill it, giving the reader a sense that Jack is a killer - whether he is a hunter, or a assassin we can tell that Jack is going to kill a living being which is later proven in the novel.