Abstract: With the acceptance of “philosophy” in Japan in the early modern times and its wide spread as the translation of “philosophy”, from the beginning of the 20th century to the 1930s, the academic circles began to explore “Japanese philosophy” and “the history of Japanese philosophy” and began to explain how “philosophy” existed in Japan’s traditional academia. However, Watsuji Tetsujirou was different from other scholars. He believed that the traditional Japanese academia before modern times was only thinking in Chinese, so he called for Japanese philosophy to “think in Japanese” and began to make an exploratory attempt to “Japanese philosophy”. Through the so-called “pure Japanese”, he tried to analyze and explain the “philosophical” meaning of “Japanese” and explore the “Japanese philosophy” which not only has the linguistic characteristics of Japanese, but also conforms to the speculative nature of “Western philosophy”. Therefore, he adopted the so-called “pure Japanese” and expressed it in the form of pure kana Japanese, centering on “あるということはどういうことであるか?” this philosophical fundamental question, launching his exploration on “Japanese philosophy”. However, in order to analyze the meaning of various language elements in this philosophical question expressed in pure kana Japanese, he had to use Chinese characters to replace the corresponding kana words for the analysis and elucidation of the philosophical meaning, making the existence of Chinese characters in his so-called “pure Japanese” an indispensable constituent element. This is the reason why he is different from other scholars and does not advocate the abolition of the existence of Chinese characters in Japanese. Because the “Japanese philosophy” he revealed only stays at the level of language, that is, “あるということはどういうことであるか?” It’s just about “how on earth to talk about what is called as the existence (being)”. This kind of “how” question is not about the exploration of “what”, and it is obviously not tenable as the fundamental question of “philosophy”.