In The Miracle Worker, how does Annie persuade Captain Keller to accept her ideas on how to treat Helen?
In Act II, Scene 2, Annie is appalled at Helen's improper behavior at the table, and she convinces the Kellers to step outside while she works with Helen.
Keller. I fail to see where you have taught her anything yet, Miss Sullivan!
Annie. I’ll begin this minute, if you’ll leave the room, Captain Keller!
Keller (astonished). Leave the—
Annie. Everyone, please.
What follows between Annie and Helen is a virtual battle of wills and the longest struggle on any stage. After removing the plates of the other family members, Annie insists that Helen use a spoon to eat her food; however, Hellen just throws the spoon down, but Annie replaces it with another. They struggle with each other until Helen finally complies with Annie's insistence that she eat properly. When Helen does seem to swallow, Annie feels good, but suddenly Helen spits out the food. Annie, then, throws water in Helen's face, and as Helen grasps, she shoves another spoonful into Helen's mouth. All this time, Annie spells into Helen's hand.
Finally after Helen yanks Annie's hair and they roll on the floor together, Helen runs out and grabs her mother's leg. Annie comes out and reports that Helen has eaten at the table with silverware off her plate, and has used her napkin.
Kate (slowly). Folded her napkin. (She contemplates the wild head in her thighs and moves her fingertips over it, with such a tenderness, and something like a fear of its strangeness, that her own eyes close; she whispers, bending to it.) My Helen—folded her napkin—
Helen's mother is thrilled with this progress; Annie's success with Helen convinces Mrs. Keller, who, in turn, convinces her husband, Captain Keller, that Ann Sullivan is capable of teaching Helen.
Annie is very blunt in the way that she challenges the Keller family about their attitudes to Helen and her disability. Above all, she is very truthful--perhaps too truthful--in what she says. Therefore when she has dinner with them and Helen begins to wander around taking food from various people's plates, Annie is the only person to stand up to this as she sees the Keller family have done this because they do want to challenge Helen and want an easy life:
It does you good, that's all. It's less trouble to feel sorry for her than to teach her anything better, isn't it?
This is very blunt and direct, but it does serve to highlight the facts about how the Keller family think about Helen and treat her. Although Captain Keller is enraged by such an attack on himself and his family, it is his wife and James who see the truth of such words and convince him to let Annie have her way in order to see if she can improve Helen's situation. Annie's strategy is therefore to speak the truth as she sees it, no matter how shocking.