Of the spotless mirrors of the holy teachings preached in His lifetime, the Lotus Sūtra is the special divine mirror. A copper mirror can show the figure of a man but not his mind. The divine mirror of the Lotus Sūtra shows not only a man’s figure but also his mind. Not only the current mind of a man but also his karma in the previous life and his reward and retribution in the future can clearly be spotlighted.
Shinkoku-ō Gosho, Sovereigns of Our Divine Land, Writings of Nichiren Shōnin, Doctrine 1, Page 177