«To Remember» - cosmichistory @ ウィキ

I guess one of the instinct we had before we entered the physical
universe is to REMEMBER and that bodies were first built as trophies to
commemorate players' victories in games.

The ability to remember is not native to a spirit. He knows rather than
remembers.

To play a game, a spirit needs to limit his ability to know. However, they
did not do a very good job in limiting players' knowingness, and players
later came to need to keep records of certain things, especially
things they had experienced or done in the games.

It's like playing a dungeon-exploring role playing game. The player plays the
game to discover new things in the dungeon and also wants to have a
auto-updating map of the dungeon so that he will not have to know again the
paths he has already come to know.