First, there are no musts, only rathers with a very high probability. Still we will use must as an abbreviation for a highly probable rather (even 1.0 probable if there are any such), because everybody is used to. I’ll give you an example how this works.
Say, that I have just moved my chess king.
- it must be my at least second move in the game
- it is rather at least my third move in the game
- it is rather late in the game
- I rather have white pieces
- I am rather losing
- it is rather not a checkmate for my opponent
- it must not be a checkmate for myself
- I am rather not a Chinese
- I am rather an Armenian
- I am rather alive
- my opponent must not have a chance to en passant in his next move
- my opponent and me, are rather males
There are certainly thousands or even millions more such rathers nobody is aware of, in the above case, alone.
The number 8, what does it mean? I am rather not Chinese anyway, they are a minority in this world. But the fact, that I moved a chess piece decreases the probability of being Chinese from 1/5 to 1/10 or even less, since the game of chess isn’t very popular in China.
I am rather not an Armenian, it is 1/1400 that I was. But that was before I made this king move. Now it is at least 1/1000 that I am in fact an Armenian. Perhaps even 1/100, due to the popularity of chess there. The probability just went up, hence the rather qualificatior now.
What about 5? Apparently I am not attacking my opponent with a rook and at least one white queen on a nearly empty board, when there is little need for me to move my king. King is not very often an attacking piece when it moves it is rather under some pressure. Not always, only the probability for such a situation is bigger. Hence the rather qualificator.
In my comment to the msjr’s comment in the previous post, I gave an example, where it will rather be two, than an ace at the river at poker.
Whatever happens, at every corner, in any situation in this world, the vast cloud of rathers, updates itself with every new bit of information coming in. Actually it doesn’t update automatically, you have to do it yourself, just like a true detective or a true scientist. You have to calculate the rathers cloud on the premise of everything you know at any moment. This way, you will function just as a true scientist should. It is impossible, I know, but you have to try it sometimes.
There are always a lot of breathtaking rathers, in almost every possible situation. Some are quite useful.