In Act 3 of The Miracle Worker, about what matter does Kate advise James?

In Act 3 of The Miracle Worker, Kate advises James to stand up to his father.

James is the son of Captain Keller, the child of a previous marriage.  He and his father do not get along well; Captain Keller looks upon James as being lazy and disrespectful, and James on his part plays the role, often using bitter sarcasm in his interactions with his father and others.  Deep inside, however, James longs for his father's approval, but is clueless as to how to gain it.  In Act 3, he apologizes to Kate for his flippant attitude, and asks for her advice concerning his father, saying,

"What does he want from me?"

Kate gives James an interesting response, observing,

"That's not the question.  Stand up to the world, Jimmie, that comes first".

Kate is telling Jimmie to look inside himself to find the confidence to make something of his life, and in that way he will win his father's respect.  Jimmy responds,

"But the world is him",

to which Kate counters,

"Yes.  And no one can do it for you".

Kate's advice is that James must reconcile his feelings about his father within himself first, and in doing this, find a sense of self-acceptance.  By becoming someone of whom he himself can be proud, James will gain his father's respect, and this is a task that he alone can undertake and accomplish.