Yong-mo Yu (1890-1981) was a supporter of religious pluralism in Korea, advocating for a syncretistic conception of God; and for interfaith spiritual renewal, during a period marked by the rejection of these concepts. A study of his work enriches our conception of the 20th century Korean Christianity. The main goal of my dissertation is to first analyze Yu's theological understanding of God and examine it in relation to the three East Asian major religious traditions as well as a Western ontological understanding of the ultimate reality; and second, through such analyses, to discuss the significance and challenges of Yu's pluralistic theology and spirituality. Yu's own definition of God as Opshi-gyeshin-Haneunim (God who exists as Non-Being) is an ontological understanding of the ultimate reality, which is very different from conservative Korean Protestantism's understanding of God. Yu's understanding of God is very similar to Robert C. Neville's understanding of God as the creator in that both of them define the ultimate reality as absolute Nothingness or Emptiness transcending both being and non-being. Yu's understanding of God was also based on the East Asian religious traditions which are Confucianism, Buddhism, and Taoism. Therefore, Yu defines Christian God as T'ai-chi and Wu-chi, nothingness, and Tao which are concepts that Yu borrows from the East Asian religions. Yu's concept of God as Opshi-gyeshin-Haneunim was formed and developed based on his own spiritual experiences, for example, his experience of spiritual union with God. At the same time, his theological reflection on the ultimate reality also had great effect on his spirituality. In the same tenor, the pluralistic characteristics of Yu's theology and spirituality are the result of Yu's creative combination of his ontological understanding of the ultimate reality transcending various religious contexts and the East Asian spirituality focusing on spiritual discipline to develop the divine power given to human beings. Yu's creative integration of the ontological analysis of God and the East Asian spiritual tradition can provide a new perspective to Korean conservative Protestantism in understanding other religions, and suggest a new type Christian spirituality in plural Korean contexts. / 2017-01-12T00:00:00Z