Many years ago he, with a firm determination to develop the revolutionary ideas of President
Kim Il Sung as eternal guiding idea of the era of independence, deeply studied the Juche idea while making a profound study and analysis of the previous theories.

In the 1970s he, confident of the absolute truth of the Juche idea, formulated the President's ideas as an integral system of idea, theory and methodology of Juche and proclaimed the program of modeling the whole society on the Juche idea.

Since then the Korean people have successfully pushed ahead with the revolution and construction, guided by the great Juche idea.

Although he was busy with the leadership over the overall affairs of the Party, army and state, he continued energetic ideological and theoretical activities to develop the Juche idea as guiding idea of the era of independence.

In March Juche 71 (1982) he made public a famous work, "On the Juche Idea," to systemize the President's ideas in a comprehensive way.

The work elucidates in a scientific and theoretical way the man-centered philosophical outlook on the world, the socio-historical outlook evolved with the popular masses, the maker of history, in the center and the guiding principles of the Juche idea. As soon as the work was published, it evoked a great public response.

Kim Jong Il authored more works such as "On Some Problems of Education in the Juche Idea" and "On Having a Correct Viewpoint and Understanding of the Juche Philosophy" and further enriched Juche-based theories of socialism.

In other famous works he advanced in an all-round way the tasks to defend and develop Korean-style socialism based on the scientific guiding idea. Typical of the works are "On Some Problems of the Ideological Foundation of Socialism" and "Socialism Is a Science".

The ideological and theoretical feats he has made for humankind and history are greatly conducive to the Korean people's effort for building a thriving nation.