The only truly ecumenical symbol of faith, the so-called Nicene Creed, outlines the reality of the Church in four adjectives (the notae ecclesiae) pointing to aspects of its nature. The Church is one, holy, catholic, apostolic. This statement about the Church occurs in the short pneumatological section, and thus makes the Church an object of belief and confessing. The marks of the Church must be somehow – in all ambiguity – manifest and answered for by the members of the Church.
1. The unity of the Church has its source in the triune God. But how and where is this unity to be perceived? Old Catholic theology would give an answer in the framework of an ecclesiology taking as its basic entity the local Church. This ecclesiology is discernible without any systematic explication in some authors writing in the 1870es (e.g. J.H.Reinkens), but a certain consistency has been attained only later, not least because of a theological exchange with voices from the Orthodox and Anglican (also Lutheran) traditions, recently with Roman Catholic advocates of a communion ecclesiology, and generally with the work of the Faith and Order Movement / Commission.
The starting point is the eucharistic community headed by a bishop; in what follows this is called the „local Church“ (i.e. traditionally speaking a diocese). A few remarks will be appropriate. The Eucharist with all its constitutive elements is the primary representation and realization of the communion of God with humans constituted in the Christ event and opened up for continuous participation in the power of the Holy Spirit. The traditional term „bishop“ designates the person who has the first responsibility for the local Church to preserve its unity, as well as its catholicity and apostolicity (see below). The bishop is, however, fully integrated in a network of distinct levels: on the one hand with the college of presbyters (usually called „priests“) and with the deacons, who together with the bishop assume the tasks of the ordained ministry, on the other hand with the non-ordained baptized, the laity, who share the responsibility for the local Church in various ways. The synodal integration of the bishop into the local Church and the participation of all ordained ministers and the laity in the responsibility for the local Church to remain the Church of God has been one of the principal concerns of Old Catholic reforms after 1870. Old Catholic theology will happily recognize a similar concern in the modern debate on episkopé and its personal, collegial and communal dimensions. It will interpret the personal dimension in terms of what may be called „monepiscopacy“ (not to be confused with „monarchical episcopacy“ and its modern associations).
A further explanation may be in place: why is it not the parish and its local congregation that serves as the ecclesiological starting point? This has to do with taking into account historical developments: e.g. the bishoprics consisting of a town and its immediate hinterland were soon superseded by bishoprics consisting of a region, the presbyters now assuming episcopal functions in the eucharistic liturgy of the local congregations. But there are other considerations. The basic unit (called local Church) ought to fulfill all its tasks as far as possible by its own capacity. For this a parish is very often too small. On the other hand there should be a limit to the circumscription of a local Church: the bishop ought to know in person those who assume responsibility in a local congregation, e.g. the ordained ministers and leading members of a parish council. If this is the case in Old Catholic dioceses that may even cover large areas it is because of their status as extreme minority Churches.
Now the local Church is a representation and realization of the One Church confessed in the Nicene Symbol of Faith, and this in a particular „place“. The extent of the „place“ is dependent on contingent factors (number of baptized, historical developments etc., see below).
2. The catholicity of the Church is to be determined in the context of the ecclesiological approach just presented. It is the local Church that carries the mark of catholicity inasmuch as it participates in God’s reality of salvation and truth encompassing heaven and earth and there finds its unifying centre. The local Church, however, does not possess catholicity for itself, like a monad, but insofar as it is in communion with other local Churches, which are equally representations of the One Church in their respective „places“.
Thus the local Churches have a soteriological-trinitarian identity – an identity, incidentally, that is to be distinguished from other identities that are marked by manifold sociocultural factors and are and should be diverse. This „theological“ identity points to the real source of the unity of the local Churches, the triune God.
This unity is manifest in the form of a communion of local Churches (i.e. dioceses), not in the form of something like a super-diocese with the dioceses thus being deficient, somewhat incomplete parts of a larger whole.
There will be communions of local Churches in various geographical extensions, up to the universal communion of local Churches. They are all representations of the One Church, each in their „place“.
From all this follows that the catholicity of the Church is not simply identical with its (geographical) universality.
3. The apostolicity of the Church is also to be seen in the context of the local Church being in communion with other local Churches. It denotes the continuity of the Church in space and time with the mission of Christ and his apostles performed in the power of the Holy Spirit. This continuity is related to the entire witness of the Church in Word and Sacrament, although some constitutive elements can be singled out, but should not be seen in isolation. The passing on of the ordained ministry by prayer and the laying-on of hands is such an element of what is called „apostolic succession“, but it must be integrated into the ecclesial context of the co-responsability of the local Church for its remaining true to the Gospel and in continuity with the Ancient Church. The apostolic succession is in the first and last analysis the process of the Church remaining identical with the apostolic foundation in all forms of inculturation and aggiornamento that will necessarily create varying identities of another order.
A clear manifestation of the apostolicity of the Church may be seen in the consecration of a bishop: he or she is elected by the local Church, ordained by bishops of other local Churches in communion with it; and in what takes place in the eucharistic context all baptized present share in the commitment of the Church to the passing on of the faith once and for all revealed and yet laid into the obedient responsibility of the Church. Two dimensions can be discerned in the event: the „horizontal“ historical continuity within the supralocal communion and the „vertical“ immediacy to God (made clear in the epicletic ordination prayer).
 Cf. Stalder, K., 1984: 110-125.
 Cf. Baptism, Eucharist and Ministry, Faith and Order Paper 111, WCC, Geneva, 1982, para. 26 (without the term episkopé); The Nature and Purpose of the Church. A stage on the way to a common statement, Faith and Order Paper 181, WCC, Geneva, 1998, para 89-106. See further Bouteneff, Peter C. and Falconer, Alan D. (eds) Episkopé and Episcopacy and the Quest for Visible Unity. Two Consultations, Faith and Order Paper 183, WCC, Geneva ,1999.
 In Germany, Switzerland, Austria, the Czech Republic, Croatia and Slovakia the single diocese covers the whole country.