§ 91. DOCTRINAL CONTROVERSIES. (1) The Adoptionist Controversy, A.D. 782-799. (2) Controversy about the Procession of the Holy Spirit. (3) The Eucharistic Controversy, A.D. 844. (4) Controversy about the Conception of the Virgin. (5) The Predestinarian Controversy A.D. 847-868. (6) The Trinitarian Controversy, A.D. 857. § 92. ENDEAVOURS AFTER REFORMATION. (1) The Carolingian Opposition to Image Worship, A.D. 790-825. (2) Agobard of Lyons and Claudius of Turin. INTRODUCTION. § 1. IDEA AND TASK OF CHURCH HISTORY. The Christian Church is to be defined as the one, many-branched communion, consisting of all those who confess that Jesus of Nazareth is the Christ who in the fulness of time appeared as the Saviour of the world. It is the Church’s special task to render the saving work of Christ increasingly fruitful for all nations and individuals, under all the varying conditions of life and stages of culture. It is the task of Church History to describe the course of development through which the Church as a whole, as well as its special departments and various institutions, has passed, from the time of its foundation down to our own day; to show what have been the Church’s advances and retrogressions, how it has been furthered and hindered; and to tell the story of its deterioration and renewal. § 2. DISTRIBUTION OF CHURCH HISTORY ACCORDING TO CONTENTS.