The purpose of this paper is to introduce Keyserlingk's theory of person and life with reference to the 1st paper "Sanctity of Life and Quality of Life -Are They Compatible ? " in Foundation of Bioethics, Tokai University Press, 1988. According to Keyserlingk, there are two decision makings toward a patient: one is a decision making based on the principle of sanctity of life and the other is a decision making based on the principle of quality of life. In popular understanding, these two principles are not compatible. However, he claims that these two principles are compatible.