All three chapters/essays are addressed to the samurai class, and all three seek to unify the spirit of Zen with the spirit of the sword.
Of the three essays in the treatise, two were letters:
- Fudōchishinmyōroku, "The Mysterious Record of Immovable Wisdom", written to Yagyū Munenori, head of the Yagyū Shinkage-ryū school of swordsmanship and teacher to two generations of shōguns; and
- Taiaki, "Annals of the Sword Taia", (太阿記) written perhaps to Munenori or possibly to Ono Tadaaki, head of the Ittō school of swordsmanship and an official instructor to the shōgun's family and close retainers.
Individually and broadly speaking, one could say that Fudōchishinmyōroku deals with technique, how the self is related to the Self during confrontation, and how an individual may become a unified whole.
Taiaki deals more with the psychological aspects of the relationship between the self and the other.
Between these, Reiroshu, "The Clear Sound of Jewels", deals with the fundamental nature of humans: how a swordsman, daimyō – or any person, for that matter – can know the difference between what is right and what is mere selfishness, and can understand the basic question of knowing when and how to die.[1]
Fudōchishinmyōroku (The Mysterious Record of Immovable Wisdom) is divided into the following sections:
- The Affliction of Abiding in Ignorance
- The Immovable Wisdom of All Buddhas
- The Interval into Which Not Even a Hair Can Be Entered
- The Action of Spark and Stone
- Where One Puts the Mind
- The Right Mind and the Confused Mind
- The Mind of the Existent Mind and the Mind of No-Mind
- Throw the Gourd into the Water Push It Down and It Will Spin
- Engender the Mind with No Place to Abide
- Seek the Lost Mind
- Throw a Ball into a Swift Current and It Will Never Stop
- Sever The Edge Between Before and After
- Water Scorches Heaven, Fire Cleanses Clouds