My inspirational concept here comes secondhand from a homily, so if I get any important details wrong, I hope Isaac will correct me in the comments. Or anyone who knows more Thomistic philosophy than I do (which is several of you).
The initial point which caught my attention was the claim that the popular American Life League slogan "You can't be Catholic and Pro-Abortion" is untrue and contains a logical fallacy. (Mind you, the intended point of the slogan is not in dispute, only its philosophical accuracy.) So the argument goes something like this:
Existence is the first act.* At baptism, our existence is ontologically changed, and we become Catholic in our very essence. Thus things like knowledge and opinions are irrelevant; we ARE Catholic in a much more fundamental sense than we are, say, American or pro-life or traditional. Even partisanship within the Church is false insofar as it separates us based on our thoughts, not our essence.
Damn those Enlightenment thinkers** (well, not really; I'd like to put a little more trust in God's mercy than that, but you know what I mean)! I have had such a thorough, solid Catholic education (thanks to my university, my friends, my parish, my reading material, etc); it scares me when I discover that I've been caught by so fundamental a lie as that.
I would like it if this post inspired some discussion. Pretty please, with sugar and a cherry on top?
*That is to say, the existence of every human being is the fundamental aspect of his personhood and is necessarily first and foremost.
**e.g., Descartes (Cogito ergo sum: "I think, therefore I am")