[按：下文是邮件笔记的内容，标题是新拟的。略有删节/修订。]

The "stardards" of reseach is of four aspects, forming a graph ——

♖    ♘

♔    ♗

King represents "simplicity" while bishop is responsible to "no redundancy"; rook makes things irreplaceable while knight is of thoroughness.

---- Thoroughness is the easiest to operate.

---- Simplicity is to consider the most basic or speical things, such as numbers 0, 1, reciprocal, square, circle, etc..

---- "no redundancy" is to remove parts, operations, etc., to reach a clever thing.

---- Irreplaceability is to make things optimal, the best or No.1.

---- The four aspects share a common spirit from the different perspectives.