First, what does cause the church to lose publicness? The author found that it was due to the lack of theology and lack of teaching about the Kingdom of God. The church has turned the Kingdom of God into the heaven, and came to think that God is of little interest in the world because God is in the heaven not in the world. Therefore, the church does not pay attention to the Kingdom of God anymore. Being separated from the world, the church has become an organization and gathering for itself and gradually lost interest in others, neighbors, and the society.

Second, what is the nature of the church? What is Public Theology? The author examined four types of ecclesiology to examine the relationship between publicness and the church: Catholic ecclesiology, Reformed ecclesiology, Free Church ecclesiology, and the WCC’s ecclesiology. It has been argued that the essence of the church is not in institutions, beliefs, or communion, but in public character through the process of changes and developments of these four types of ecclesiology. Also, the author has introduced four models of public theology according to the church's public practice while taking a position to participate in the publicness of the society within a Christian identity among them.

Third, what kind of kingdom is God's one according to the Old and New Testaments as a whole? What does affect the restoration of publicness when you see the Kingdom of God through such a way? The author proposes a theoretical alternative using Byungho Zoh's kingdom of priests and Kingdom of God. The kingdom of priests represented throughout the Old Testament has five characteristics. The kingdom of priests was a country that started with a Passover lamb, led to the temples and the elders, had forgiveness and share resources with neighbors as well as peace between the nations. The Kingdom of God from the New Testament also has five characteristics. It was a nation which began with the Lamb of God, was realized through the cross, and led to the churches and disciples. And it is the nation where one soul is more precious than the world, and God is called the Father. This understanding of the kingdom of priests and the Kingdom of God strongly shows the intercession between the world and God which is the essence of the publicness that the church should possess.

Lastly, what was the result that preaching of the Kingdom of God applied to the ministry? The author gave sermons on the Kingdom of God to the young adult group of the church where the author worked for, and the young who heard the sermons responded that they learned the Kingdom of God biblically and God's love for the world, and the fact that the nature and purpose of the church lie in its publicness.

Researches carried out through this project can be very useful tools to restore the lost publicness of the church. The author hopes that this project will be a conduit to make the church the church in the truest sense and to make the church respond vigorously to God's will and purpose for the world.