Since Schleiermacher, in nineteenth century, liberal theologians neglected the doctrine of the Trinity. However, on the basis of the Hegelian influence, leading 20th century theologians, Barth, Moltmann, Jüngel and Pannenberg revitalized the doctrine of the Trinity. This revitalization was however based on a re-interpretation of the Nicene theology, in which vital elements of Nicene theology and its reformed affirmation were altered by their approach to the doctrine of the Trinity. Reformed doctrine of the Trinity is based on the Nicene formulation of the doctrine of the Trinity. In order to make a reformed assessment of this revitalization of the doctrine of the Trinity, one first has to attend to its Nicene formulation. Nicene theologians interpret the doctrine of the Trinity on the basis of the Scripture against heresies. Athanasius confirms not only the Son’s ‘homoousia’ with the Father, but also the Spirit’s homoousia with the Father. In this regard, Athanasius protects the deity of the Son and the Spirit. Basil and the two Gregories follow Athanasius. They also apply the term ‘homoousia’ to the Spirit. Especially, the Cappadocian theologians set the following formula of the doctrine of the Trinity: One essence, three hypostaseis. For them, according to the particularity of their attributes, the Father, the Son and the Holy Spirit are distinguished, however, according to their common essence, there is one God. Their main idea is that the three hypostaseis are equally God. They focus on the deity of the Son and the Holy Spirit against Arians and Pneumatomachians. They strongly emphasize the unity of nature or essence of God on the basis of the priority of theologia over economia. <ol> <li> Karl Barth’s starting point is the revelation of God. For him the doctrine of the Trinity is three repetitions of God himself: Revealer, Revelation, and Revealedness. Barth identifies the the immanent Trinity with the economic Trinity. From this, his Christology always refers to the ensarkos Logos. And he uses the term ‘Seinsweise’ instead of the term ‘person’.</li> <li> For Moltmann, the content of the doctrine of the trinity is the crucifixion of Christ itself, and the form of the crucified one is the Trinity. He focuses on the passibility of God. He also identifies the immanent with the economic Trinity. His social understanding of the concept of divine Person is based on panentheism.</li> <li> As with Moltmann Jüngel concentrates on the ‘death of God’. For him, the theology of the death of God is based on Luther’s theology of the cross. The Christian doctrine of the triune God is the epitome of the story of Jesus Christ. With Barth and Moltmann he identifies the immanent Trinity with the economic Trinity.</li> <li> Pannenberg’s doctrine of the Trinity implies the divine self-disclosure in Jesus Christ. His Christology is ‘from below. And Pannenberg’s concept of person is the reciprocal relationship between persons.’ He confirms the identification of the immanent Trinity and economic Trinity.</li> <li> Modern understanding of the doctrine of the Trinity on the basis of Panentheism differs from the Reformed tradition which emphasizes the distinction between the immanent Trinity and economic Trinity, and uses the notion of person as a metaphor of the distinction.</li></ol> The doctrine of the Trinity is closely connected with the Church since it is constituted by the Triune God. Therefore, the implications of the doctrine of the Trinity are important for practical church life.