Teaching manual for first-year students of the Department of Theology at A.P.TH., candidates for entrance exams, and those who wish to learn what Theology is and its timeless study in Higher Schools in the East and West until today. The book by the professor of the Department of Theology at A.P.TH. is divided into two parts: In Part A, the terms Encyclopedia, Introduction, and Theology are examined, as well as Higher Schools in the East, the formation of the University during the Middle Ages in the West, and the teaching of Theology. Also, its scientific nature, its prospects in the modern university, and its significance for society. Part B presents texts by contemporary theologians, on the characteristics of Theology, its relationship with the Church, the patristic tradition, scientific methods, time, space, and the cultural environment in which theological thought is cultivated. In the Epilogue, aspiring researchers can find brief useful guidelines for the preparation of scientific papers.