What if the person is really asking a question that's different than the question that they verbalized? The notion of 'telling the truth' seems to change.
If there is a choice, do you answer the question that they have in their head, or do you answer the question that they have posed in front of you? It seems to me that one would want to do the former even if it means 'lying' with respect to the question that they have actually asked you.
Granted, this means that you'd better be damn sure that you know what question they have in their heads or what they're after, or that you can probe them and ensure that you can figure out what that question is..
These verbalized questions may be different than the actual 'in the head' questions because of insecurities, fears, politeness, not wanting to be a bother, and plain ol' human nature.
For example, you're at a carnival with someone. They're enjoying themselves, and you still kinda want to stick around but you are also sort of tired. They are empathic and they sense that you're getting tired, but they would also believe that your being tired would make you want to go home.
So, they ask, "Are you tired?" Let's treat it as a yes/no question, because it's fun that way. Chances are that if you were to say "yes," they'd take it to mean that you want to leave, so you would opt to say "no." Are you being dishonest by saying "no," or are you being truthful with respect to what you really believe that they're asking?
Let's allow nuances. "Yeah, but I'm having fun" or "Yeah, but not enough to go home" even seem like the other person may feel undue sympathy for you--that they would wind up ignoring the fact that you would want to keep going. This reeks of 'not trusting the other person with what you might say,' but I haven't explored it very much.
Ah, communication. I guess this would be considered one of those white lies?