"First of all, I have seen the Magisterium referred to as the Living Magisterium, which gives me the impression that it is a forever changing thing. That parts of an augmented Faith may be added to it, defunct or what would be considered outdated parts of the Faith can be taken away."
Doctrine can develop in the terms of deepening of understanding, however, it can never change to the extent that future developments contradict or negate Traditional doctrine. Also meanings cannot be spun - the meaning that the Church has always had of a particular doctrine is the meaning that must stand for all time. Vatican I's De Fides et Ratio is critical for a correct understanding of the limits of doctrinal development:
13. "For the doctrine of the faith which God has revealed is put forward
not as some philosophical discovery capable of being perfected by human intelligence,
but as a divine deposit committed to the spouse of Christ to be faithfully protected and infallibly promulgated.
14. Hence, too,that meaning of the sacred dogmas is ever to be maintained which has once been declared by holy mother church, and there must never be any abandonment of this sense under the pretext or in the name of a more profound understanding."
This is an infallible Decree of an Ecumenical Council which reinforces its doctrine with the following Canons:
"4. On faith and reason
1. If anyone says that
in divine revelation there are contained no true mysteries properly so-called, but that
all the dogmas of the faith can be understood and demonstrated by properly trained reason from natural principles:
let him be anathema.
2. If anyone says that
human studies are to be treated with such a degree of liberty that their assertions may be maintained as true even when they are opposed to divine revelation, and that
they may not be forbidden by the church:
let him be anathema.
3. If anyone says that
it is possible that at some time, given the advancement of knowledge, a sense may be assigned to the dogmas propounded by the church which is different from that which the church has understood and understands:
let him be anathema.
And so in the performance of our supreme pastoral office, we beseech for the love of Jesus Christ and we command, by the authority of him who is also our God and saviour, all faithful Christians, especially those in authority or who have the duty of teaching, that they contribute their zeal and labour to the warding off and elimination of these errors from the church and to the spreading of the light of the pure faith.
But since it is not enough to avoid the contamination of heresy unless those errors are carefully shunned which approach it in greater or less degree, we warn all of their duty to observe the constitutions and decrees in which such wrong opinions, though not expressly mentioned in this document, have been banned and forbidden by this holy see."
Hopefully the above decrees will answer your following questions:
"Let's say that 10 years from now, based on what science has reliably affirmed, the Church proclaims homosexuality to be an acceptable variant of human sexuality, and for all intents and purposes elevates it to parity with heterosexuality. Am I obliged as a Catholic to accept this teaching?"
No! It would be contrary to Scripture, Tradition and 2,000 years of consistent Magisterial teaching. Homosexual acts are sins abhorred by God and any Pope or bishop who taught otherwise would be a heretic, apostate and abomination, and by virtue of your Baptism and Confirmation as a soldier of Christ you would be obliged to reject their teaching and fight against it.
"If I had children and wanted to rear them in the Faith, would obedience to the Vicar of Christ require that I instruct my children according to the new development?"
No! For the same reasons. Our obedience is always to God first, and if any Pope felt himself mighty enough to trample the Word of God and the Divine Law, then he should be resisted and not obeyed.
"Also, on another thread today, there was a picture of a Mosaic ostensibly of a female Bishop. The Mosaic is somewhere in Rome. I think the thread title was Pope Joan. Do you know anything about this?"
If its "Episcopa Theodora" that you are referring to, then its most likely that she was the wife of a bishop. Western Catholics tend not to think of the obvious, because we like to pretend that all the clergy have been celibate since the time of the apostles! This is, of course, not true. However, even if all the Latin clergy had been celibate, you will note that the lady concerned has a Greek rather than a Latin name.
Even today in the Greek Catholic Churches, the female suffix is often still appended to a rank of clergy to give a clergyman's wife a title.
Consequently my Melkite deacon friend is the "diakonus" (Greek for deacon) and his wife is the diakonissa (deaconess). Episcopa Theodora was probably the wife of a Greek bishop. The Greeks don't have married bishops these days - married men are only allowed to progress to the diaconate and priesthood - however they certainly used to, as several of the bishops took their wives to the Council of Nicea.
That's my opinion of her anyway! ;)
They really did, and thank you.
And it was "Episcopa Theodora", and you're right the thought of her possibly being a Bishop's wife never crossed my mind.