I stated that conservative Catholics only accept revision of Church teaching when it emerges from within the tradition and higher up in the hierarchy of truths. I think, in practice at least, there is an exception to this: conservative Catholics will accept revision to Church teaching based on clearly demonstrated scientific or historical facts.
For instance, I don't really know that the biblical creation account was ever taught definitively and formally as being literally true, but I'm pretty sure that it was more or less taken for granted that it was so until clear evidence emerged to the contrary. Similarly, with medieval geocentric cosmology. Likewise, I think that at least some of the conclusions of modern critical biblical scholarship (e.g. regarding authorship of the biblical books) are in this category. And, at least in this case, there were preliminary negative responses to these ideas from the Vatican--though nothing ex cathedra. While it's true that that these new facts were able to be assimilated because there was not clear, definitive teaching to the contrary and openings could be found within the tradition, it remains the case that what was assimilated was new information from outside the tradition.
Perhaps, then, what differentiates liberals from conservatives within the Church, to some extent at least, is that certain developments in modern society and thinking that conservatives view as errors to be rejected or resisted are held by liberals to be in this category of clearly demonstrated empirical truths--so the felt needs of the day are new "facts" that traditional teachings have to be weighed against. For example, the difficult situation of civilly divorced and remarried people is a new (or newly recognized) fact that in some way relativizes the authority of the anathemas of Trent. Likewise, modern psychology gives us new facts that force us to adjust traditional understandings of sin and culpability.
Things at this level involve conceptual errors about the meaning of moral truth and too slavish following of modern expert opinion claimed in the name of science and complete servility to the modern political order ... but it can still be seen as a difference in degree rather than in kind from the sort of development that a conservative would view as possible. In other words, not necessarily heresy.
However, many liberals tend to accept modern "facts" that work at a meta level to negate the tradition as a whole: so they also say that the facts of comparative cultural anthropology undermine any attempt to posit a universal, idea of unchanging human nature, making the teaching of universal moral truths impossible in principle; the facts of modern historical research force us to reject the naive idea that the tradition is continuous and binding; and the facts of post-modern Cultural Marxism force us to subject the entire narrative to critique in the name of the oppressed and marginalized.
This, surely, is the synthesis of all heresies.
