It is said that there are so many possible games of chess that if a game were to be completed every second, there have not been enough seconds since the Universe began to complete all of the possible games. That is how variable chess is.
On the other hand, the rules of chess are absolutely fixed. A bishop moves like this, not like that; a knight does something of its own – it’s not allowed to move like a castle. If you play by any other rules, you are not playing chess. That is how fixed chess is.
Some people think that the rules of life are as strict and laid-down as the rules of chess. Wouldn’t that make our decisions simple?
In real life, there are not necessarily sixty-four squares on the board. Some of them are black and some white, but lots of them are grey. Some of the pieces are of different colours and play on loan to Black or White, and change sides without notice. Some change shape over night and decide to move differently, or wander off for a beer. Some gang up against their own side, or refuse to play with one another because they’ve fallen out.
That’s how variable real life is.