Based on the previous studies of relevant issues,this paper is an attempt to explore the aptly neglectful topics in the recent studies of the"Four-line Doctrine",the purpose of which is to clarify the following aspects:1)the historical and cultural background in which the Neo-Confucianist four-line doctrines evolved;2)the difference and similarity between Zhang Zai's"Four-line Doctrine"and Wang Shouren's"Four-line Doctrine";3)the historical process of the Neo-Confucianist subject-object unification embodied in the four-line doctrines from the Song to Ming dynasties.Logically,Neo-Confucianism went on the path from the mutual inclusion of subject and object to the absolute unification of them in its development."The Four-line Doctrines"were products in the historic and cultural background of Chinese Buddhism,its intention and feature changing with the development of times;from the Northern-Song-dynasty Neo-Confucianism to the Ming-dynasty Neo-Confucianism,"the Four-line Doctrine"converted from the subject-object dichotomy of enterprising and responsible Confucianists to the subject-object unification of conscience-acquiring and perfecting Confucianists.Therefore,the application of the dichotomic formal logic to the studies of Neo-Confucianist four-line doctrines might not be essentially the right method to understand its philosophical height as it intends to develop Neo-Confucianism through Buddhism and embrace Buddhism in Neo-Confucianism.