It is no use quoting from some Russian theologian’s or hierarch’s words to the effect that the partitions separating the Christian churches do not reach the heavens: the fact of the West’s falling away from the Church in 1054 is for the Orthodox believer a present fact of religious experience… [Y]ou adduce the viewpoint of the famous Metropolitan Philaret of Moscow, Philaret, who wrote in one of his early treatises: “No church which believes Jesus to be the Christ will I dare call false.” But there are quite a few obstacles to recognizing as valid Metropolitan Philaret’s reasoning that churches can be either pure truth or of impure truth. A church of impure truth seems to me to be evidently a false one, and there cannot be a false church; such a church ceases to be a church, becoming an extra-ecclesial community. For Metropolitan Philaret did not partake of the Eucharist with the Latins; and neither do other theologians of ours, who occasionally show too much zeal in defending the unacceptable doctrine of the unity the Church, according to which the one Church may embrace local churches that have for centuries been out of communion with each other. And this looks inconsistent to me. Why then shouldn’t one celebrate the mass or partake of the eucharist with a priest of the local Roman Church?
No, the falling away of Rome from the Church (or of the East from Rome) is a fact on hand, which should not be hushed up and reduced to zero. (The Unity of the Church and the World Conference of Christian Communities)