Japanese teacher: So the ‘sou desu’ form is used when you want to say something seems like something else. Like, Tanaka San seems happy — you could say ‘Tanaka San wa ureshisou desu.’
Student #1: What if he’s smiling and he just won the lottery? Would you have to say he seems happy, or could you say that he is happy?
Japanese teacher: Well, you are not Tanaka San — he could find the money to be a burden — so you’d have to use ‘sou desu.’
Student #2: What if he’s yelling that he’s happy?
Japanese teacher: He could be lying. You never know with Tanaka San… –Columbia University Overheard by: Vicksburg