That's a neat explanation, Snail - I think it is equivalent to some given above, but more concisely expressed.


I went off on my particular tangent to address how it comes about that two people (namely the original player and the newcomer) can both see exactly the same physical situation (two closed doors and one open showing a goat), yet have different probabilities of getting the car. It is subtle, but I think it worth puzzling through because it isn't anything like as obvious(!) as the basic problem, and it does show that information is as important as the physics.