Originally posted by shavixmir
Yes. I agree.
Let's assume you pick a door with salt.
Now, if you switch, there are two possibilities. Imagine the presenter does NOT open a door for you.
One possibility is that you get the Porche, one is that you keep the salt. If you switch, you have a 50% chance of Porche, assuming Salt was the first pick.
But the presenter DOES open the door for you. That means that if you switch, you will DEFINITELY win - assuming you lost in the first place, which we already agreed you probably did. Do you agree?
Summarized - if you pick salt the first time, which you probably will, and the presenter shows you a door with salt, then the last door must be the porche, because you know where the two piles of salt are (one of them you're not sure about, but you think you know where it is - behind your first pick).
When people say you "have more information" because of the door opening, the information is "Psst - don't pick this door, if you pick it, you'll lose".
If you know one way to lose, you can avoid it and make it easier to win.