The role of probability in solving the Monty Hall problem

[robvalue]

The host knows where the prize is. The host must open a door so that it doesn't reveal the prize, and isn't your door. There is no lying, how could there be?

You get to see that the door has nothing behind it. Well, you should anyway. That's the point.

EDIT: Yes, the original question in this thread says he opens a door. So you see that there's nothing/ a goat. Where does lying come in?