In Christendom, while the doctrine of salvation through mechanical obedience was retained, the authority of a Church was substituted for that of a Code of Law.

The growth of the idea of Humanity, as opposed to that of mere nationality, made this necessary.

As the former idea began to compete with the latter, the need for a divinely-commissioned society which should declare the will and communicate the grace of God, not to one nation only but to all men who were willing to hearken and obey,--and whose action, as a channel of intercourse between God and Man, should be continuous rather than spasmodic,--began to make itself felt.

A Code of Law might conceivably suffice to regulate the life of one small nation; but when we consider under what varying conditions of climate, occupation, custom, tradition, and so forth, the general life of Humanity is carried on, we see clearly that no one Code can even begin to suffice for the needs of the whole human race.

Hence, and for other reasons which we need not now consider, the West, in accepting the philosophy of Israel, translated its master idea of salvation through mechanical obedience into the notation of ecclesiastical, as distinguished from legal, control.
That obedience to a supernaturally-commissioned Church, or rather to the One supernaturally-commissioned Church, is the first and last duty of Man, is the fundamental assumption on which the stately fabric of Catholic Christianity has been reared.