Originally Posted by

**kiskrof**
There are obviously several ways of explaining this problem. The more intuitive to me is "trying" to pick a wrong door as first choice. I am 67% to succeed. The interesting thing about this problem is that it helps understand that probability do not exist in the the world in a situation like this, where everything is already in place when you start playing.If you choose randomly, your probablity at the second choice is 50%, (you are 50% likely to be 67% likely to win and 50% likely to be 33% likely to win, numbers work), but from the point of view of a competent probabilist observing you after you have chosen but before you open, you are either 67% to win or 33% likely to win. However, you are either 100% or 0% to win from the point a view of an omniscient observer. Average is always 50%! Does real probability exist in the world when we throw a coin? Whatever your answer to this question, the probability of you guessing the result of the coin throw will be 50% (unless you have some superpowers). So probabilty does not depend on the nature of the universe, but is a property of our representation of the world.