My friend used Isaiah 24.5 to justify the Mormon doctrine of the Great Apostasy. "The earth also is defiled under the inhabitants thereof; because they have transgressed the laws, changed the ordinance, broken the everlasting covenant." She says that when people started changing ordinances, which they believe are basically the sacraments... marriage, baptism, communion, confirmation, etc, they fell into apostasy and God took the Church to heaven. But so, what are ordinances in the Catholic Church?I hope you'll excuse me if I offer a better question instead: What is Isaiah referring to here and how does it apply to Catholic Christianity?
The Navarre commentary is very helpful:
24:1-27:13. This third section of part one of the book of Isaiah contains texts of different sorts, but mainly visions and eschatological oracles. Many scholars call this section the "Apocalypse of Isaiah", or the "Great Apocalypse" as distinct from a later, shorter section (34:1-35:10) of a similar type, usually called the "Little Apocalypse". The "Great Apocalypse" is made up of a collection of eschatological oracles that was given its present form after the Babylonian exile. They announce the sentence that the Lord will pass on the whole world, describing in great detail the cataclysms of the "day of the Lord". At the very end, after a catastrophe of cosmic proportions, God will reward the righteous with the messianic banquet that marks the definitive victory of the righteous scattered throughout the nations. Interspersed among these oracles are lyrical poems in praise of God's special providence towards his people and their victory over enemies and oppressors.Now, here's what I think we take from all of this. Since Isaiah 24 is part of his "Great Apocalypse" about the end of time, the description of those who break the covenant (v. 5) is a foreshadowing of those who will be found transgressors of the New Covenant when Jesus comes again.
24:1-23. The oracles addressed to the nations (13:1-23:18) revealed God's judgment against each nation; now, this terrible oracle announces a chastisement that will affect the whole cosmos. It speaks of the entire population of the world being destroyed (vv. 1-3); of the effects of this on all living things (vv. 4-16;); and of the ultimate destruction of the earth and all that it contains (vv. 16b-23).
The oracle speaks of a cosmic catastrophe affecting the entire earth and even the heavens (v. 4)--all because men have transgressed the laws and broken the "everlasting covenant" (v. 5). This latter probably means the covenant with Noah (Gen 9:8-17); because men have failed to keep it, it weighs as a curse that will bring down upon them all kinds of misfortune, from which only a small remnant will escape (v. 6).
As we already saw (in the accounts of the origins of the world), when mankind went about its business without reference to God, it was scattered across the face of the earth (cf. Gen 11:1-9). Here, too, the city is emptied and left desolate (vv. 8-12). Even so, in the midst of universal desolation, there are those who joyfully sing of their deliverance (vv. 13-20), as happened in the exodus after the crossing of the Red Sea. On "that day", too, as at the time of the Flood, the Lord will reveal his power by punishing sinners, while also manifesting his glory as he reigns from Jerusalem (vv. 21-23).
The "west" (v. 14), in Hebrew the "Sea", means the Mediterranean and by extension the west. The "host of heaven" (v. 21) refers to the stars, regarded as gods in the Assyrian-Babylonian myths.
With this understanding, we find that your friend is wrong on two counts: one, because Isaiah is referring to the end of time, not to a "Great Apostacy" in the early Church, and two, even if this were referring to a falling away of the true faith early in the history of the church, your friend is begging the question by saying that this applies to Catholicism. In other words, you have to believe that the Catholic Church has contradicted the true faith before you can claim that this verse applies. This your friend has yet to prove.
So, the task of your friend is to prove that the Church has really fallen away. This he will be hard-pressed to do. For one, no matter what date he assigns for when the Church apparently fell away, you'll be able to find testimony from Christians before that date that attests to Catholic beliefs. Secondly, to say that the Church has ever fallen into doctrinal error is to basically call our Lord a liar when he said that the gates of hell will not prevail against the Church (cf. Mt 16:18) and that He will always be with the Church, until the end of the age (cf. Mt 28:20).
I hope that helps