How do you know?
1. How did you get that information? (A straightforward question. The stress in on know.) Bill: The train is about to pull into the station. Sue: How do you know? Bill: I hear it. Fred: I have to apologize for the coffee. It probably isn't very good. Jane: How do you know? Fred: Well, I made it.
2. Inf. What makes you think you are correct?; Why do you think you have enough information to make this judgment? (Contentious. The heaviest stress is on you.) Bill: This is the best recording made all year. Bob: How do you know? Bill: Well, I guess it's just my opinion. Tom: Having a baby can be quite an ordeal. Mary: How do you know? Tom: I read a lot.