In his Newsweek column, Andrew Sullivan launches a chivalrous attempt at defending the indefensible:
There was a time not so long ago when Catholics and other Christians weighed various moral claims to find a balance. Sometimes, the lesser of two evils was preferable. For centuries, for example, Catholic theologians, including the greatest, Thomas Aquinas, argued that human life begins not at conception but at some point in the second trimester.
It almost goes without saying that Thomas Aquinas possessed not a clue as to when human life begins. He was merely regurgitating whatever Aristotle guessed at, from which evolved a Western intellectual system of oppressive philosophical theocracy that retarded real advances in human thought and human welfare for centuries.
But, let us grant Sullivan his point. What, then, does the modern Church say? Well for Heaven's sake let us also proceed to Catholic.com, which rather helpfully publishes a metaphysical "Answers" page (and I kid you not):
How does [Thomas] square with current Catholic teaching against abortion from the time of conception?
Notwithstanding his belief in delayed animation and ensoulment, Aquinas still taught that abortion was wrong from the moment of conception. He believed it to be a mortal sin expressive of a homicidal will, even if in the early stages of pregnancy, as he thought, homicide isn't actually committed.
See? There's no conflict with Thomas, so gotcha -- which the Church always will, for the Church, you see, is infallible, as indeed virtually all churches and all formal belief systems and all doctrine always are. For they remain akin to medieval Aristotelianism as enfolded in Belief: they don't really want you asking questions, even if they've already the answers ... Every last one.
Which is why I viscerally rebel not against faith, for Reason can underlie Faith (as Thomas also believed) -- but against organized religion ... Every last one.