> Catholicism teaches that Divine Revelation is God's Self-Revelation and therefore can't change
Revelation may not change, but the actual concrete beliefs of the Catholic Church manifestly do.
> Again, if it changes, then it isn't true.
If it changes, and it was claimed to be a universal constant, than either the before- or after-change version isn't true, sure, that's trivially true.
I said
>> The objection to your point is that the teachings of Christianity are timeless if true.
To which you said
> "The teachings of Christianity" are, in fact, not consistent across time or across subsets of Christianity at the same time
> Revelation may not change, but the actual concrete beliefs of the Catholic Church manifestly do.
The teaching of the Catholic Church just is revelation. Individual Catholics or churchmen may believe all kinds of things, some contrary to revelation and/or each other, but that's something distinct. What has manifestly changed?
> The teaching of the Catholic Church just is revelation.
No, even in the view of the official teachings of the Catholic Church, the teachings of the Catholic Church include, but extend well beyond, revelation.
If the teachings were only what was understood to be unquestionably part of the content of revelation, then there would be no teachings which were not dogmas.
Yes, that was a bad way of putting things on my part. You are correct. Better would be "the basis of the Catholic Church's teaching, and the primary part of its teaching, is revelation".
To return to the main disagreement:
>> The objection to your point is that the teachings of Christianity are timeless if true.
> "The teachings of Christianity" are, in fact, not consistent across time or across subsets of Christianity at the same time
The teaching of the Catholic Church, insofar as it is proposed as being part of Revelation, or as following logically therefrom, is timeless and unchanging. One reason is that Revelation is primarily about God (it's His Self-Revelation), who can't change.
Again, the fact that different Catholics believe different things (contrary to Revelation or each other), or that some teachings that are not proposed as being part of Revelation change over time, is irrelevant to this.
Obviously, if you claim Revelation is an "abstract ideal", then you are implicitly claiming it's false, or doesn't exist, which is an entirely different argument.
Are there any teachings that are proposed as part of Revelation, or as following logically therefrom, that have manifestly changed over time?
Precisely.
Here is an article[0] explaining papal infallibility that touches on some of these things in greater detail for those interested.
[0] http://edwardfeser.blogspot.com/2015/11/papal-fallibility.ht...