Searching for an answer to the problem's posed by the contemporary ecumenical movement, the author turns to the original sources of the patristic eccle- siology. One of the key positions in this traditional ecclesiology is held by St. Irenaeus of Lyons. The author emphasizes the catholic (integral) vision of the Church and all her constitutive »elements«. Thus her apostolicity, the apostolic succession, her faith (truth) and Eucharist have for St. Irenaeus a »catholic« character. All these three elements constitute one reality of the divine »economy« of salvation in Christ. In other words, these three elements form together the apostolic tradition of the Church. The over-emphasis of one of these elements or neglecting of one of them destroys the catholic character both of the apostolic tradition and each of these elemets.
Hence, the genuine koinonia whith the Church includes in itself simultaneously the participation with all the three elements. According to St. Irenaeus, the Church without Orthodoxy or without Eucharist is not the Church; Orthodoxy (right belief) outside the Church and Eucharist is unthinkable as well; the Eucharist also outside the Church and the right belief cannot exist.
Drawing conclusions from St. Irenaeus’ premises, the »inter-communion« as it is today preached in some ecumenical circles, is outright impossible, because the »inter-communion« would undermine the uniqueness of the Church and character of all her constitutive elements. The author accepts the necessity of ecumenism in time also, not only in space, as it was already recommended by the eminent Orthodox theologian Father Georges Florovsky.