Doctrinal development or doctrinal negation?

One of the most popular arguments of "recovering" Catholics is that the Church, which claims to teach infallibly the "faith once delivered to the saints," has so changed some key doctrines as to negate them and thus undercut her claim to infallibility. "Progressive" Catholics, while often unwilling to go that far, are also prone to argue that doctrinal change in the past has been of such a kind as to supply ample precedent for the changes they want to see today. For the sake of the Church's credibility, I believe it's very important to rebut both arguments.

I've been doing so for months at Pontifications. If this is the sort of thing that interests you, go to my latest article on the subject. It contains, besides a reply to the latest challenge from the blogosphere, links to all my previous articles on the topic.