The Unfettered Mind (不動智神妙録, Fudōchi Shinmyōroku) is a three-part treatise on Buddhist philosophy and martial arts written in the 17th century by Takuan Sōhō, a Japanese monk of the Rinzai sect.
The book is a series of three discourses addressed to samurai but applicable to everyone who desires an introduction to Zen philosophy, the book makes little use of Buddhist terminology and instead focuses on describing situations followed by an interpretation.
Its contents make an effort to apply Zen Buddhism to martial arts.
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: Sōhō refers to many poems and sayings, including those of: