In chapter 28, Jim is captured by the pirates, who want to kill him for his part in thwarting their plans. Long John Silver is among them and hears Jim speak boldly, saying that if they spare his life, he will promise to help them when they are on trial. He also says he has seen enough men die by this time to not fear death. Silver defends Jim and tells the others to stay away, saying,

I like that boy, now; I never seen a better boy than that.

When the other men go out to decide what to do, Silver says quietly to Jim,

I'll save your life—if so be as I can—from them. But, see here, Jim—tit for tat—you save Long John from swinging.

Silver shows he is a shrewd judge of character and of situation. He does genuinely like Jim, because he sees that he is both bold and a person of his word. He realizes, too, that the other pirates are fools and their cause is hopeless, so he wants to cut his losses.

Silver believes Jim when he says he will help the others if they helped him. As Silver says, he will do what he can to save Jim's life if Jim promises to help him later. He warns Jim that the other pirates are ready to force him to walk the plank. Jim accepts the offer. He is less naïve than he used to be, but he has faith that Silver can help save him.

In this way, Silver essentially saves Jim out of self-interest by striking a bargain with him.