From the beginning of Ender’s Game, it is well established that Peter is dangerous. Even when he was only ten years old, Peter was feared by his siblings. Valentine and Ender both knew that he “was a murderer at heart,” though “nobody knew it” but them.

Much of Peter’s hatred is directed at Ender. After all, Ender is a reviled Third, his birth only authorized because he is meant to succeed where Peter failed. Yet Ender is not the only target of Peter’s wrath. Whether it is because Valentine dares to protect Ender or simply because it is his nature, Peter threatens to kill his sister as well. Valentine, however, has two powerful means by which to protect herself from her older brother. The first is Peter’s own self-interest. The second is her gift of persuasion.

Valentine knows that Peter was capable of terrible things. He threatened both his sibling’s lives, tormented former schoolmates, and tortured the squirrels in the woods. But she also knows that he, like herself and Ender, possesses both great intelligence and immense self-control. He will not act out in “a fit of rage ... he always, always acted out of intelligent self-interest.” Knowing this, Valentine can use it to her advantage.

This is demonstrated in the the novel’s first confrontation between the siblings. Peter threatens to kill first Ender and then Valentine and to make it look like an accident. Valentine is able to diffuse the situation by reminding Peter of his own ambitions. “You don’t mean any of it,” she tells him, “because you want to be in government someday. You want to be elected.” How can he possibly accomplish that goal if there is any suspicion that he is involved in the mysterious deaths of his own siblings?

Valentine knows Peter will not act on his more destructive impulses unless the benefits outweigh the risks. This knowledge is her armor: “to keep herself safe, all she had to do was make sure it was more in Peter’s interest to keep her alive than to have her dead.” Perhaps this is a contributing factor in her decision to help Peter with his Locke and Demosthenes project. He makes it clear that if she won’t help him, he might truly become the monster she thought him to be—“like the bad ones,” as he describes it. As one of the bad ones, she will be a likely target of his wrath.

If Peter’s own sense of self-preservation is a shield for Valentine, then her ability to empathize and persuade is her sword. She is able to influence others with her words—as Peter says, “Val could always see what other people liked best about themselves, and flatter them.” This gives her great capacity for manipulation. She can “not just control what they did” but also “in a way, what they wanted to do.” She is clever, empathetic, and able to turn others to her own point of view.

Even though Peter knows this about her, she is even able to persuade him sometimes. She attempts this during the first confrontation between the siblings, when Peter finds out about the removal of Ender’s monitor—she “tried to soothe him before he had time to strike.” It is not enough to stop him then, but Val learns as she gets older. She is always able to make sure that Peter believes she is useful enough not to harm. Thus, she agrees to help him with his Locke/Demosthenes project, not only because the project itself intrigues her but because helping Peter ensures her continued value to him.

She recognizes that he is manipulating her into helping him and is “only pretending to share power” as they proceed with their new endeavor. Still, even this understanding protects her and gives her an advantage. “You are only pretending to share power with me,” she thinks of her brother, “but in fact I have power over you. Even though you don’t know it.”