Wang Yangming told the story about himself, which is what makes it useful. As a young man, taking seriously Zhu Xi's instruction that one extends knowledge by investigating things, he and a friend resolved to investigate the bamboo in his father's courtyard and find its principle. The friend concentrated on it for three days and fell ill; Wang persisted for seven and made himself ill as well, and they concluded they lacked the capacity to be sages. Years later, in exile at a remote post station in Guizhou, he reached the conclusion that the method had been wrong rather than the men: principle is not in the bamboo waiting to be extracted, it is in the mind, and the investigation of things means rectifying the mind's engagement with them. Everything in his philosophy — innate moral knowing, the unity of knowledge and action, the sufficiency of the mind — follows from that reinterpretation. It is the rare case where a philosophical school can be traced to a specific documented failure.