Just to stir the pot a little... Catholic conservatives frequently distinguish between disagreeing with the Church's views on abortion/gay marriage/stem cell research and a departing from the Church's views on the death penalty/torture/war/economic justice. The idea, as then Cardinal Ratzinger laid out in his July 2004 letter on receiving communion, is that the former are intrinsically evil, whereas the evil of the latter positions depends on some degree of prudential judgment:

For example, if a Catholic were to be at odds with the Holy Father on the application of capital punishment or on the decision to wage war, he would not for that reason be considered unworthy to present himself to receive Holy Communion. While the Church exhorts civil authorities to seek peace, not war, and to exercise discretion and mercy in imposing punishment on criminals, it may still be permissible to take up arms to repel an aggressor or to have recourse to capital punishment. There may be a legitimate diversity of opinion even among Catholics about waging war and applying the death penalty, but not however with regard to abortion and euthanasia.

There are lots of questions about this distinction that have been raised here and elsewhere. I don't want to get into those again in this post. My question is a different one. What are we to do when a Catholic politician seems to reject the principle underlying the prudential judgment? For example, there may be "legitimate diversity of opinion" about waging THIS particular war or applying the death penalty in THIS particular case. But what if the politician rejects the broader exhortation to "seek peace, not war"? Surely -- in the magisterium's view -- there is no room for legitimate diversity of opinion on that more general matter of principle. Similarly, while there may be a great deal of legitimate diversity of opinion concerning how best to promote the well being of the poorest, surely (on the magisterium's view of its own authority) there is no legitimate diversity of opinion concerning the mandate to structure social policy toward that end. Thus, a Catholic politician who said that he was structuring social policy precisely because government has no obligation towards the poorest, could not be said to differ from the Church on a matter of mere prudential judgment.I take it no one would disagree with the foregoing. Perhaps my next assertion will be more controversial. I think it is fair to hold political figures to some standard of plausibility in the empirical assertions underlying their prudential judgments. And where their empirical claims are utterly lacking in empirical foundation, then it is fair to say that they are likely lying when they claim that their prudential judgments represent an effort to conform their reasoning to certain moral principles. I assume, for example, that if a Catholic pro-choice politician says that he accepts the Church's teaching on abortion but that he believes that legally prohibiting abortion will increase the abortion rate and so opposes legal prohibition for that reason, pro-life Catholics would argue that he is acting within the boundaries of a "legitimate diversity of opinion." At a minimum, I think they would require some significant empirical support to back up his claim before they would concede the good faith of his prudential judgment.On similar grounds, it seems to me that the Ryan plan -- and Ryan himself -- can plausibly be accused of simply disregarding basic principles of Catholic social thought, not just prudential judgments about how best to achieve those principles. At the most basic level, the structure of his plan -- cutting taxes for the wealthiest and for corporations while slashing benefits for the poorest and most vulnerable -- does not square with the Church's mandate to structure social policy in a way that is fundamentally focused on the well-being of the poorest, a kind of maximin principle. Still, the argument might go, this sort of restructuring of government's operations could be reconciled with Catholic principle if it were the case that massively cutting taxes for the rich and increasing the economic burdens on the poor would stimulate the economy to such a degree that the resulting prosperity would create a rising tide that would lift all boats. This was, I assume, the purpose of citing to the Heritage Foundation study predicting that the Ryan plan tax cuts would increase revenue and would produce incredibly low levels of unemployment. Now that the Heritage study has been pretty universally rejected, however, what is the case for structuring a debt reduction plan along the lines of the Ryan plan? Can the debunked supply-side logic of self-funding tax cuts and the associated trickle-down prosperity justify Catholic support for a plan with the features of the Ryan Plan as consistent with the preferential option for the poor? It seems to me that that can be the case only if we impose absolutely no burden of plausibility on the empirical assumptions underlying prudential application of those principles. [In the absence of evidence to the contrary, we should simply interpret the plan as intending to do what it does: improve the situation of the best off and then making up for that (and, in addition, reducing the debt over the long term) at the almost exclusive expense of some of the most vulnerable. And such an intent runs contrary to the principles of Catholic social teaching -- it does not reflect the prudential application of those principles.]And, frankly, as for Ryan himself, I don't see why we should give him the benefit of the doubt. As is well documented, the man is a ardent admirer or Ayn Rand. He requires his staffers to read Atlas Shrugged. And he has credited Rand with his decision to enter public service. Rand's objectivist philosophy rejects the notion that the government has any obligation to help the poorest. Rather, its purpose is to protect rights of private property and enforce market transactions in order to unleash the most creative and gifted among us.In trying to interpret Ryan's motives, we have a couple of choices. On the one hand, we can say that he's trying to help the poorest, notwithstanding any empirical evidence that his plan will do that. On the other hand, we can say that he's implementing Rand's anti-Christian objectivist philosophy, which he has credited with motivating him to enter public service. [He's either blinded to empirical reality by his ideological commitments and actually believes we make the help the poor by handing money to the rich and cutting health care for the poor, or he's intending to do what his plan straightforwardly seems designed to do -- reduce state-imposed burdens on the rich and let the poor fend for themselves.] It seems to me that, given the evidence about his admiration for Rand, the most plausible interpretation is the latter. There's no question that his plan, if implemented, would dismantle two of the pillars of the post-War welfare state (Medicare and Medicaid) while putting more money in the pockets of the wealthy. But if Ryan's purpose is to move us closer to the objectivist ideal espoused by Rand, then it seems to me that he is beyond the boundaries of legitimate prudential disagreement. He is applying principles that directly contradict those of Catholic social teaching.[I've updated the post slightly, with the substantive changes in brackets.]