The debate on the yan–yi relation was carried out by Chinese philosophers collectively, and the principles and methods in the debate still belong to a living tradition of Chinese philosophy. From Yijing (Book of Changes), Lunyu (Analects), Laozi and Zhuangzi to Wang Bi, “yi” which cannot be expressed fully by yan (language), is not only “idea” or “meaning” in the human mind, but is also some kind of ontological existence, which is beyond yan and emblematic symbols, and unspeakable. Thus, the debate on the yan–yi relation refers firstly to metaphysics, secondly to moral philosophy, and then to epistemology and philosophy of language. Guided by this view, this paper recalls the source of the debate on the yan–yi relation to Yijing and Lunyu, distinguishes four meanings of “yi” in Chinese philosophy, and reconstructs three arguments. These arguments are the “yan cannot express yi fully” argument, “forget yan once you get yi” argument, and “yan can express yi fully” argument. Finally, this paper exposes and comments on those principles, methods and the general tendency shown in the debate from the following five aspects: starting point, value-preference, methodology, texts (papers and books), and influences.