Kim Gu (1876 – 1949) was one of the leaders and the last president of the Provisional government of the Republic of Korea, which was located in China in 1919 – 1945. He was also one of the political leaders who played important role in the process of establishing of the Republic of Korea after 1945. During his life in exile in China he has written a personal diary, describing his life in connection with the Korean independence movement. At the present time the diaries by Kim Gu are published in modern Korean language and they are a very popular source for studying both the private life of Kim Gu and Korean independence movement in general. The paper describes the diaries “Baekbeom Ilji” (Recordings by Baekbeom made in solitude) and discusses a number of the methodological problems helping to get the proper knowledge from writings of this type. They are: 1) Categories of historical facts: “simple” (describing events and objects of material world) and “complicated” (describing spiritual activities of human bein