SUMMARY Taking as a point of departure the provisional aspect of Christian eschatology which determines the pilgrim Church in its very essence, the writer draws on several examples (the condemnation of Modernism, the encyclical Humae vitae, the Nota explicativa praevia of Vatican I) which within our Church point in an opposite direction, namely towards maintaining its identity, its creed and its hierarchical structure as unchangeable. Is this not, however, neglecting the provisional aspect of the Church's eschatological „identity”? And does this agree with historical reality? An honest scientific comparison, for example, of the important decree Haec sancta of the Council of Constance with the dogmatic pronouncements of Vatican I concerning papal jurisdictional primacy and infallible magisterium brings to light two clearly opposed convictions concerning the relation of Pope and General Council (Church community). Still there can be no doubt as to the validity and binding power of Haec sancta. To attempt to cover up the contradictions between Vatican I and Constance F. Oakley calls „desperate attempts at rapprochement”, and rightly so. One begins with the dogmatic a priori: there can be no real contradiction between Haec sancta and Pastor aeternus, thus there is none. Historical honesty, however, forces one to the opposite conclusion: there is in fact contradiction, therefore it can be there. But what then remains of the identity of the Church guaranteed by Christ Himself? In four points the writer tries to define more exactly this identity. 1) The Church is in its very essence defined by the eschatologically provisional character of „the People of God under way”, which brings with it—inside the history of the one and the same Church—historically demonstrable changes. 2) The Church is human salvation history, in which continuity goes together with the most crass discontinuities. „A frightening gulf separates the Church of today from the original constitution of the Church” (Küng). 3) This discontinuity can also affect time-bound structures and time-bound dogmatic pronouncements which in another era have not yet or no more the salvation meaning and salvation value which precisely give them their force and their truth in a later or earlier age. 4) Because these „defects” are the consequences of the provisional aspect of the Church's eschatological nature, its essential identity is not impaired, but rather made clearer to us as to content. Who will ever be able to grasp completely and fix for good the identity of a Christian or of the Christian Church! As essentially human salvation history the pilgrim Church is never finished. It is time and again with the working of Christ's Holy Spirit creatively actualized, made young and recreated by ourselves. And it is—sometimes only after laborious, patient, faith-filled searching, with much experimentation and falls and come-backs—described and contained in provisionally tenable formulas and institutional frameworks. The only thing that stands fast is that this identity must be and remain conformed to the original salvation message of Jesus Christ, which in final analysis is Himself; but this will always be the case if this identity continues to spring from the „faith of the Church”, in which the salvation message and in which Jesus Christ Himself is present and at work. The „unfathomable riches of Christ” (Eph. 3:8) and consequently also of His Church will only be revealed at the eschaton. The ecclesiology of our fundamentally new era must put aside its old, wrongly supposed „safe” positions. It has to set itself with Christian „spiritual freedom” to the laborious task of developing a fundamentally new concept of Church that genuinely corresponds to the existing present-day „faith of the Church”. Otherwise, will it not fall seriously short of a believing realization of the eschatological „provisionality” of the Church and consequently of the essentially provisional character of ecclesiology itself? The real problem that our Church now faces is nothing less than the Church itself. Thence comes the urgent quest for an essentially provisional ecclesiology.