- I believe you.
- I believe in you.
Can 1 and 2 both be used to mean
- I believe that what you said is true.
I have seen 1 used to mean 3, but is that usage idiomatic. Also, I know that 2 sometimes is used to mean to trust someone because you think that they can do something well or that they are a good person, But can't it also be used to mean 3?