"Sitting in Meditation" (ching-tso) is a central issue in Neo-Confucianism. The practice of sitting in meditation is usually related to the doctrine of "emphasizing tranquility" (chu ching). The doctrines of "emphasizing tranquility" and "sitting in meditation" became an important issue in the Neo-Confucian tradition after Chou Tun-i propounded the doctrine of "emphasizing tranquility" and Chi'eng Hao and Ch'eng I promoted the practice of "sitting in meditation" Ch'en Hsien-chang's creation of a special way of sitting in meditation inspired a new intellectual orientation toward the study of the Learning of the Mind, and the issue aqttracted increasing scholarly attention. Besides Ch'en Hsien-chang, many other Ming scholars, including Chan Jo-shui, Wang Yang-ming, Nei Pao, Ou-yang Te, wang Chi, Lo Hung-hsien, Kao P'an-lung, Ch'en Lung-cheng and Liu Tsung-chou, involved themselves in discussion of the issue. This study uses Liu Tsung-chou's reconsideration of the doctrine of "emphasizing tranquility" and "sitting in meditation" as a case-study to reveal four main kinds of doubts on the doctrine of "emphasizing tranquility" and the practice of "sitting in meditation" in the history of Ming Neo-Confucianism. First, there was doubt about the compatibility between these doctrines and the doctrine of "emphasizing reverence" that was emphasized in the Ch'eng-Chu paradigm of Neo-Confucianism. Second, there was doubt about their closeness to Ch'an Buddhism. Third, there was doubt about the "substance/tranquility" and "function/activity" dualism on which they were based. Last, there was doubt about their lapsing into a preference for tranquility over activity. From this study we can investigate how the doctrines of "emphasizing tranquility" and "sitting in meditation" developed in Ming intellectual history.