Physical, earthly, unity of the faith is central to the physical Catholic church. The schism permanently destroyed that to show that the church is invisible. Communion takes place across the physical organizational boundaries.
Cardinal Newman on One Church
…There is such a thing as religious truth, and therefore there is such a thing as religious error. We learn that religious truth is one—and therefore that all views of religion but one are wrong. . . . our religious creeds and professions at this day are many; but Truth is one: therefore they cannot all be right, or rather almost all of them must be wrong. That is, the multitude of men are wrong, so far as they differ; and as they differ, not about trivial points, but about great matters, it follows that the multitude of men, whether by their own fault or not, are wrong even in the greater matters of religion.
…Doubtless if men sought the truth with one tenth part of the zeal with which they seek to acquire wealth or secular knowledge, their differences would diminish year by year. Doubtless if they gave a half or a quarter of the time to prayer for Divine guidance which they give to amusement or recreation, or which they give to dispute and contention, they would ever be approximating to each other. We differ in opinion; therefore we cannot all be right; many must be wrong; many must be turned from the truth; and why is this, but on account of that undeniable fact which we see before us, that we do not pray and seek for the Truth?
…Some men will tell us that this difference of opinion in religious matters which exists, is a proof, not that the Truth is withheld from us on account of our negligence in seeking it, but that religious truth is not worth seeking at all, or that it is not given us. The present confused and perplexed state of things, which is really a proof of God’s anger at our negligence, these men say is a proof that religious truth cannot be obtained; that there is no such thing as religious truth; that there is no right or wrong in religion; that, provided we think ourselves right, one set of opinions is as good as another; that we shall all come right in the end if we do but mean well, or rather if we do not mean ill. That is, we create confusion by our negligence and disobedience, and then excuse our negligence by the existence of that confusion. It is no uncommon thing, I say, for men to say, “that in religious matters God has willed that men should differ,” and to support their opinion by no better argument than the fact that they do differ; and they go on to conclude that therefore we need not perplex ourselves about matters of faith, about which, after all, we cannot be certain.
…How are the sheep of Christ’s flock scattered abroad in the waste world! He came to gather them together in one; but they wander again and faint by the way, as having lost their Shepherd. What religious opinion can be named which some men or other have not at some time held? All are equally confident in the truth of their own doctrines, though the many must be mistaken.
(Parochial and Plain Sermons, Vol. 8, Sermon 13: “Truth Hidden When Not Sought After,” 1843)
