However, John's comment impelled me to go back and reread Humanae Vitae, and I have to say I'm mystified that there could be any question of whether it's a reformable teaching.
First, if you read the Magisterium's reply in HV 6, it's clear that the Holy Father does not accept the findings of the commission convened to discuss the matter:
However, the conclusions arrived at by the commission could not be considered by Us as definitive and absolutely certain, dispensing Us from the duty of examining personally this serious question.
So the question fell to the Magisterium to settle. Pope Paul VI then notes several points:
- This teaching has been constant from the earliest days of the Church (and earlier) and conforms to natural law. (HV 11)
- This teaching is the promulgation of the law of God Himself. (HV 20)
- Since the Church didn't make this teaching up, She cannot be its arbiter and can only guard and interpret it. (HV 18)
John's NFP website points to some of the early Scriptural references to contraceptive methods, as well as the early Church's prohibitions against pharmakeia (sorcery), which many consider to be a reference to abortifacient herns or medicines (Galatians 5:20; Revelation 9:21 and 18:23. The Didache also makes reference to pharmakeia as well.
This teaching has all of the marks of dogma, except for the formal declaration.
I'm still looking for an explanation from the camp that claims this teaching to be reformable. John's essay points out a few claims, but most of these seem like the kinds of smoke and mirrors used by those pushing for women's ordination—in large, delay and denial tactics.
What was missing from Humanae Vitae was a definitive statement. HV 14 declares the position, but without a clear statement in the kind of faith with which the faithful need to hold this teaching, the question will continue to be unanswered in the minds of many.
The Code of Canon Law, canon 749 §3 makes it clear when a teaching is to be taken infallibly: "No doctrine is understood as defined infallibly unless this [a clear declaration that something is to be definitively held] is manifestly evident.
I think a definitive statement on the matter is overdue.