In the nineteenth and early twentieth centuries, numerous Western missionaries were involved in debating the existence of God in various religious texts and practices in ancient China. Drawing on both the rising philological scholarship in Europe and their own field experience in China, the Western missionaries examined the idea of God, the Thearch, and Heaven as the Supreme Being in the spiritual life and ritual activities of the Chinese people. From the Christian perspective, they attempted to identify the original belief in one God in ancient China in order to convert their Chinese audience. Furthermore, they addressed the issue of monotheism in the broader Asian context by suggesting the universal monotheistic degeneration from Persia to China across Asia continent.