Does anyone know the answer to this riddle?

Ok, so a friend got me stumped with this one, and I have yet to figure it out. Perhaps the collective could help me out?

You are in a room. There is no possible way out, except for two doors. One leads to a fulfilling life, and the other to damnation and death. In front of you stands only one man in white robes. He knows which door leads to which. You have only one question to determine two things: One; is the man trustworthy and honest? Two; which door leads to the fulfilling life?
What question do you ask?

I was able to determine that the robes mean nothing.
I did get this far with him: I said that a question would be, “Would you please open this door for me?” I thought that was it, BUT, he doesn’t have to open the door. And you can’t force him to.

So, the question stands: what do you ask the man?