It's hard to express,but two example:1)难道他是一个好人？This sentence means you are not sure if he is a kind man,but you think he isn't. 2)难道他不是一个好人？This sentence also means you are not sure if he is a kind man,but you think he is a kind man.
June 25, 2013
Don't you think he is accountable for this incident ? =(you suggest) He should be accountable for this incident