I've been thinking about this for a while. Humans seem to be immune to moral argument. This was occasioned by Barack Obama's speech ostensibly asking for dialogue on the issue of abortion. There will be no dialogue, of course, since he himself said that the differences are irreconcilable. They certainly appear to be. But why?
It is puzzling for pro-life people why there has been so little movement. Why don't people change their minds? The science is clear. Ethically, it seems obvious that if man is ever worth protecting under the law, he must be worth it in the womb, since there is no substantial change. If humans acquire dignity as a result of some power of reasoning, then we never acquire dignity at all. I've been over this before, but no one ever seems to be convinced.
Because humans are not entirely rational. We make decisions on the basis of desires and pleasures, and our desires and pleasures and intellect have been disordered by sin. We have trouble thinking clearly, especially when the res is something close to us. We are fallen, and can't think our way up.
But don't just take my word for it. Look at what Plato does in the Republic. He wants to talk about justice, but can't do it, because his audience is not ready. The common wisdom about justice is so faulty that any attempt to reach justice itself is doomed to failure. It is only after the soil is prepared over the whole book that the interlocutors can attempt the ascent out of the cave.
Look at what Aristotle does in the Nichomachean Ethics: he attempts to determine the nature of happiness, and decides that it is good rational activity. Then, he avoids talking about what kind of activity it is, rather spending much time speaking of virtues. But how can one speak of virtues without knowing what they are virtues for? It doesn't make sense, unless he was tailoring the discussion to the audience, only presenting contemplation as true happiness at the end, when presumably they would be more ready to hear it.
But we don't argue that way any more. We don't even argue. There will be no debate on abortion, only soundbites and caricatures. Given the limits of our attention span, how could we convince anyone else of anything important?
I need to think about this more.