I learned to play ping-pong and tennis that way. By myself.
I learned to play ping-pong against a backboard.
I learned to play tennis against a wall.
Learning to play tennis against a wall is perfect. The wall forces you to be balanced because the wall is balanced (left and right).
The wall let you see the other side of the net, albeit slower.
The wall immediately reflects your flaws.
I am revisiting this concept because I am re-learning Vietnamese by myself. I don't have a "dance partner". I can do a lot by myself.
I can learn by "kata" like in Karate. A book is a kata. Chess games in a book is kata. That is easy. I can spar with computers.
Can I spar with my clone? Hmm.
People do do this as an exercise. Actors who play twins in a movie. They talk, fight, and interact with "themselves".
All by myself. Sounds like a Celine Dion song.
I have thought about this on an off for decades.
The first time I've heard about this is at a party. I brought Gomoku. We played. Nobody has seen it before. The best player at the party (besides me) and I talk.
He noticed that the game is deceptively simple. Key word is deceptive.
He also plays chess, but doesn't like it. It is the same every time.
He plays a game called Warhammer. One he rolls the dice and moves for one side. The next day, he rolls the dice and moves for the other side! That is the first time I've heard of such a thing.
I've also heard it from Kung Fu novels. Some crazy guy has black hair one side of his head and white hair on the other side. And he uses his hands to fight each other, each hand fighting with a different style. But that is fiction.
My first thought, and still for the most part, is that this cannot be done.
Because, chess has an element of "I know something you don't know". Ironically, it has elements of poker. Elements of hidden hands (even though everything is on the board and nothing is hidden). It has elements of deception, guile, and bluff.
You cannot play chess against yourself because the traps would not work.
I've played chess where I let the fianchettoed bishop capture my Rook by "surprise", to attack the weakened holes without the bishop.
I've moved my Queen in front of the other Queen, and the other guy backed off his Queen. It was pure bluff.
In playing other people, and computers, we essentially are playing against ourselves, but not exactly.
If I were to play myself, I cannot deceive myself. What would the advantage and disadvantage be?