In a fascinating exercise in sophistry, Charles C. Camosy, associate professor of theological and social ethics at Jesuit-run Fordham University,makes the case that Catholics can in good conscience vote for a candidate who professes to be a socialist, advocates same-sex marriage, works against religious freedom and insists on women’s right to abortion.

Much of Comosy’s argument relies on the idea that since no candidate is perfect, none should be excluded in a person’s conscientious choice of whom to vote for. No one issue–or group of issues–should disqualify a candidate. While one candidate may be for the killing of the unborn—the reasoning goes—another one may be cold-hearted toward immigrants, soft on gun control, indifferent toward the poor or too much a hawk in foreign policy.

It is popular among the enlightened classes to denounce so-called “single-issue” voting as the unsophisticated stance of the uneducated.

In point of fact, however, whether they are willing to admit it or not, all Americans believe in single-issue voting; they only disagree on when to apply it. No one disagrees that certain issues carry so much weight that they make or break a candidate’s suitableness to govern. They merely disagree on whether issues like abortion carry that much weight.

If a candidate came forward and said he believed that women are fundamentally inferior to men, for example, most would see that as sufficient reason not to vote for him. It wouldn’t matter at that point what his foreign policy looked like, or whether his economic program seemed superior to his opponent’s, or what he thought about education reform.

In this hypothetical situation, it also wouldn’t matter how much his sexist worldview would practically influence legislation and national policy.

So despite the fact that his archaic beliefs couldn’t possibly triumph over more clear-headed legislators and, after all, a president doesn’t have the power to abrogate women’s suffrage or bring back discriminatory labor policies. It wouldn’t matter. Almost no one would want a sexist president speaking in a representative way for the republic or naming Supreme Court justices or serving as commander-in-chief.

There are many other such single-issue litmus tests that would immediately disqualify a presidential candidate — such as overt racism, anti-Semitism or the opinion that all the elderly should be forcibly euthanized at the age of 70. Even if they got everything else right, these “single issues” would rightly be enough to kill their chances.

So, the question that Mr. Camosy seems unwilling to address head-on is whether abortion is this sort of evil. For those who understand abortion to be the murder of an innocent human being in a mother’s womb, it is hard to see how the abortion issue would not tip the scales for or against a candidate.

Mr. Camosy gets around this delicate issue by dealing what he believes to be a decisive blow to radical pro-lifers: the issue of care for the poor. In the spirit of Pope Francis, Camosy suggests that attention to the poor is absolutely central to Catholic social ethics and without it, everything else falls flat.

Moreover, he declares, “Sanders’ commitment to the poor blows away any GOP candidate.” Ergo, Sanders is a viable candidate for conscientious Catholics.

As in the case with every sophist, however, Camosy’s logic is fatally flawed.

First, as the legacy of Marxism, it is a typical practice among the left to identify the “poor” with a socio-economic class, an error that has been repeatedly denounced by the Catholic Magisterium. While material poverty is indeed a great evil that must be eradicated, the “poor” comprise all the defenseless, vulnerable and oppressed among us, especially those without a voice.

First among the poor are the unborn. To allow them to be systematically destroyed by the millions under the guise of legality is an unspeakable evil, leading Pope Francis and Patriarch Kirill to declare Friday: “The blood of the unborn cries out to God.”

In his typically blunt style, Saint John Paul II wrote in regard to abortion and its relationship to other rights:

How is it still possible to speak of the dignity of every human person when the killing of the weakest and most innocent is permitted? In the name of what justice is the most unjust of discriminations practiced: some individuals are held to be deserving of defense and others are denied that dignity?

Take a person who is willing to eliminate unborn children because they are “inconvenient” and you will quickly find that their so-called interest in helping the poor is nothing more than a word game.

Second, even if he weren’t pro-abortion and pro-gay marriage, how can Sanders be said to “blow away” any Republican candidate in his commitment to the poor?

There is an enduring liberal fallacy that those who speak most about the poor are the ones who care most about the poor, and that a powerful social assistance state that redistributes wealth is truly the best option for the poor.

Many thoughtful citizens believe that a social assistance state that creates an ongoing dependence on government hand-outs with no long-term strategy for lifting the poor out of poverty is not in the best interest of the poor and indeed does not respect human dignity.

Catholic social doctrine, in fact, has always insisted on Christians’ responsibility to assist the poor, but has carefully avoided canonizing particular programs or systems for doing so. A legitimate diversity of opinion on how best to help the poor is very much a part of the Catholic tradition. (Diversity of opinion on abortion is not.)

Curiously, for a professor of social ethics who presumably has some familiarity with Catholic social teaching, Camosy never mentions that fact that socialism has been repeatedly condemned by the papal Magisterium as completely incompatible with the Christian understanding of the human person and society.

After socialism was condemned by Pope Leo XIII in 1891, a number of concerned Catholics approached Pope Pius XI 40 years later and asked him to reevaluate socialism to see whether in a more mitigated form it might be compatible with the Christian worldview. Cannot socialism be “baptized”? they asked.

Pius famously responded:

Whether considered as a doctrine, or an historical fact, or a movement, Socialism, if it remains truly Socialism, even after it has yielded to truth and justice on the points which we have mentioned, cannot be reconciled with the teachings of the Catholic Church because its concept of society itself is utterly foreign to Christian truth.

And he concluded: “Religious socialism, Christian socialism, are contradictory terms; no one can be at the same time a good Catholic and a true socialist.”

Perhaps it is not necessary to be a socialist in order to vote for one, or to support abortion in order to vote for someone who does, or to favor gay marriage in order to support a candidate who does.

But a person must eventually ask, if I am willing to sell out on the issues that matter most, what is left?

Follow Thomas D. Williams on Twitter @tdwilliamsrome