The Lutheran catechism says: "The church is holy Christianity, or an assembly of all believers, under Christ, their chief, in which the Holy Ghost through the Gospel and the sacraments offers, communicates, and secures divine salvation," meaning, by this, that the Catholic Church has gone astray and has fallen away, and that the true tradition is preserved in Lutheranism.
For the Catholics the divine church coincides with the Roman hierarchy and the Pope. For the Greek Orthodox the divine church coincides with the establishment of the Eastern and the Russian Church.[8] For the Lutherans the divine church coincides with the assembly of men who recognize the Bible and Luther's catechism.
Speaking of the origin of Christianity, men who belong to one or the other of the existing churches generally use the word "church" in the singular, as though there has been but one church. But this is quite untrue. The church, as an institution which asserts of itself that it is in possession of the unquestionable truth, appeared only when it was not alone, but there were at least two of them.
So long as the believers agreed among themselves, and the assembly was one, it had no need of asserting that it was the church. Only when the believers divided into opposite parties, which denied one another, did there appear the necessity for each side to assert its authenticity, ascribing infallibility to itself. The concept of the one church arose only from this, that, when two sides disagreed and quarrelled, each of them, calling the other a heresy, recognized only its own as the infallible church.
If we know that there was a church, which in the year 51 decided to receive the uncircumcised, this church made its appearance only because there was another church, that of the Judaizing, which had decided not to receive the uncircumcised.
If there now is a Catholic Church, which asserts its infallibility, it does this only because there are the Græco-Russian, Orthodox, Lutheran Churches, each of which asserts its own infallibility, and thus rejects all the other churches. Thus the one church is only a fantastic conception, which has not the slightest sign of reality.
As an actual, historical phenomenon there have existed only many assemblies of men, each of which has asserted that it is the one church, established by Christ, and that all the others, which call themselves churches, are heresies and schisms.
The catechisms of the most widely diffused churches, the Catholic, the Orthodox, and the Lutheran, say so outright.
In the Catholic catechism it says: "Quels sont ceux, qui sont hors de l'église? Les infidèles, les hérétiques, les schismatiques." As schismatics are regarded the so-called Orthodox. The Lutherans are considered to be heretics; thus, according to the Catholic catechism, the Catholics alone are in the church.
In the so-called Orthodox catechism it says: "By the one church of Christ is meant nothing but the Orthodox, which remains in complete agreement with the œcumenical church. But as to the Roman Church and the other confessions" (the church does not even mention the Lutherans and others), "they cannot be referred to the one, true church, since they have themselves separated from it."