This article starts with a thought that the ideas of ‘Eol’(soul) and ‘Gugeo’(national language) presuppose each other. Given that ancient history was the place of struggle in which the desires of a modern nation-state were projected, national language was an important tool of the struggle for nationalist historians such as Shin Chaeho and Jeong Inbo, who attempted to reveal the reality of ancient history. At the same time, the history of national language could only be established based on national history. In order to take a critical look at this entangling of ‘national history’ and ‘national language’, this article analyzed Jeong Inbo's “Joseon's Eol of 5,000 Years”. Chapter 2 examines the specific aspects of the linguistic methodology Jeong Inbo used in “Joseon's Eol of 5,000 Years” and its status in his research on Korean history. Chapter 3 reviews Jeong Inbo's approach to describing ancient history, which introduced a linguistic methodology, in the academic context of the time and show that it was an important tendency of ‘Joseonhak’(Korean Studies) that sought to eventually find "Something true to Korea." Chapter 4 examines the correlation between the ideas of ‘Eol’ and ‘Gugeo’, which originated from ‘Guksu’ and ‘Gukon’.

Abstract
1. 들어가는 말
2. 정인보의 ‘얼 사상’과 언어학적 방법론의 도입
3. ‘조선적인 것’의 시원을 찾아서 고어의 복원과 고대사의 —구축
4. ‘얼’, 혹은 ‘국어’의 사상이라는 근대적 문제설정
5. 나가는 말
참고문헌

• 김병문(연세대 근대한국학연구소) | Kim Byungmoon