1. Weak: John comes from the Savage Reservation and doesn't like what he finds in Civilization.
Better: Because of John's unusual origins, he doesn't like and can't adapt to life in Civilization.
Explanation: The original sentence states a fact, while the improved version claims a cause and effect relationship that the essay's writer could show with evidence and analysis.
2. Weak: Chief Bromden gets to learn a lot of secrets because people think he can't talk.
Better: Chief Bromden spends years taking in others' secrets by pretending to be a deaf mute, but eventually realizes that he will get more out of his life if he interacts with others.
Explanation: The first states fact while the improved version gives the essay's writer something to demonstrate in the essay.
3. Weak: While claiming to be honest, Iago tricks everyone around him.
Better: Because of Iago's reputation for honesty, he manages to ruin several lives.
Explanation: If your thesis statement has only fact, you'll have nothing to demonstrate in your essay.