The Double Effect Principle:
A Primer for Confused Catholic Democrats*

Nothing hinders one act from having two effects, only one of which is intended, while the other is beside the intention.” —St. Thomas Aquinas, “Summa Theologica, II-II, Qu.64, Art.7″

Before I was a Catholic I was a liberal Democrat (that’s right, upper case D).  I ceased to be a Democrat in the early 1990s because I could no longer convince myself that the party’s support of abortion was morally correct. At that time I didn’t know that some Catholic politicians and theologians were using their own versions of the Double Effect principle to justify non-opposition to abortion.  My naive liberal view then was that if you didn’t grant the right to life to the unborn, that most basic right to the most defenseless of all humans, your fight for justice was  hypocritical in the extreme.


As I began (at the ripe age of 65) to learn more about politicians and their ways, I discovered that they  used all sorts of rationalizations to justify politically expedient positions. For example, Mario Cuomo (the intelligent one, Cuomo, pere) said in an address at Notre Dame University (as quoted in “This Week”):

I protect my right to be a Catholic by preserving your right to believe as a Jew, a Protestant, or non-believer, or as anything else you choose…We know that the price of seeking to force our beliefs on others is that they might some day force theirs on us.

I find that argument disingenuous in the extreme.  Moral principles are supposed to be universal. Had Mario Cuomo opposed forced Sunday attendance at Mass, then his argument would be appropriate, or had he been Muslim opposed prohibiting pork, also appropriate.  But the sanctity of life is a universal moral precept.   Would you say that opposing human sacrifice is wrong because it violates the beliefs of a Satanist cult?

Other Catholic politicians use arguments that supporting aid to poor families is a way of making children “wanted” and thus minimizing abortion.  This is the so-called “seamless garment” position, which maintains an equal level of importance to opposing abortion, capital punishment, nuclear war, economic injustice, man-made global warming, etc., etc.


Now, there are ways a politician can maintain a position that is nominally “pro-life,” but is still effectively pro-abortion. One can call for the repeal of “Roe vs Wade,” can vote for banning partial-birth  or late-term abortion but vote against confirming judges who are likely to be  pro-life, vote for financial support of abortion agencies, etc., etc.

Senator Bob Casey, Jr (from my state, Pennsylvania) is a master of this tactic.  He has spoken for repeal of Roe vs Wade (what would “repeal” be, judicially?), has voted to make abortion illegal 20 weeks after conception (by the way, how do you determine that date exactly?).   On the other hand he has voted 75% of the time since 2011 for measures supported by Planned Parenthood and 100% of the time in 2016 and 2017 for legislation supported by NARAL Pro-Choice America.

When questioned about such support, Casey and other Catholic Democrat senators reply that these measures  support women’s health.   Balderdash!

Let’s now examine a moral principle that might guide Catholic politicians of either party, the double effect principle.


I’ll not discuss the double effect principle extensively.   The Stanford Encyclopedia of Philosophy gives a lucid, detailed account, as does Fr. Faulkner’s blog post, linked below in the NOTE.  Go to the featured image to see these basic points illustrated:

  1. The act in and of itself must not be morally evil.
  2. If the act yields a bad effect, one must not intend for this bad effect to happen.
  3. One must intend for the act to have some specific good effect.
  4. The bad effect must be a “side effect;” it should not cause the good effect.
  5. The good and bad effects must be appropriately “proportional;”  that is to say, you should not do something which brings about a minor good and a major bad event.

Here is an example often used to show how the double effect principle might be applied to a moral conundrum:

A pregnant woman has cancer of the uterus.  The only medical procedure that can save her life is to excise the uterus with the cancer;  of course, this will kill the foetus.    Since the intention is not to kill the foetus but save the woman, this procedure does satisfy the double effect requirement #2 above, as well as the others.   (I assume that if the procedure would not be carried out both the woman and foetus would die.)

Note the difference from the following example: let’s suppose the fetus has some characteristic such that if the pregnancy is carried to term, the mother may get very ill or die (for example, Rh factor before medication was known?).  The double effect principle would not sanction aborting the foetus to save the mother.   This action would violate requirement #4, above.

Having laid down the conditions to be fulfilled for the double effect principle to be satisfied, I’m going to pose several political examples and ask you, dear reader, to think about whether  the double effect principle would be satisfied if the action is carried out.  I’ll not give my own opinion;  however, let me emphasize that I think some of the actions below are or would be morally correct, even if they don’t meet all the requirements for satisfying the double effect principle.


Voting for Donald Trump (2016, 2020;  I’ll note that until 2:35 pm, 15 November, 2016, I was a Never-Trumper and had planned to vote for the Libertarian—what’s his name?—but decided that would effectively be voting for HRC and so at 2:37 pm, voted for Trump.   I haven’t regretted it, despite reservations about Trump’s character.)

  • Killing Soleimani;
  • Impeaching Donald Trump for wearing a MAGA hat at the 2021 State of the Union address;
  • Voting for Appropriation Bills that support both Planned Parenthood and Health Care for the poor;
  • Blackmailing “liberal” senators to get them to support nomination of a conservative Supreme Court Justice;
  • Leaking a false report about a conservative nominated for high administrative or judicial post.

There are undoubtedly others, but space is limited.   How about giving a few in comments?


*The featured image is taken from a blog by Fr. Joseph Faulkner on applying the double effect principle to voting.

More to explorer


  1. Killing Soleimani – sadly some people deserve to die. Actually, we all deserve to die because we’ve all committed Deicide (my AA sponsor of 30 years ago and his sponsor, my priest confessor, told me I was in that class); nevertheless, people like Soleimani and Saddam Hussein and Osama Bin Laden are in a special case. I don’t like that and I’m not blood thirsty, but there it is.

    Impeaching Donald Trump for wearing a MAGA hat at the 2021 State of the Union address; – go Donald!

    Voting for Appropriation Bills that support both Planned Parenthood and Health Care for the poor; – I don’t like this, but these Appropriations Bills are so huge that anathema things are almost always mixed in with good things (like the wheat and the tares). I got no good answer for this one. Thankfully I am NOT President (or in a position to decide anything, including in my own household unless I get concurrence from the Filipina Matriarch in charge).

    Blackmailing “liberal” senators to get them to support nomination of a conservative Supreme Court Justice; – no, this is wrong and unnecessary. Just tell the truth about these liberal senators. That’s sufficient to ruin their lives.

    Leaking a false report about a conservative nominated for high administrative or judicial post. – no, this also is wrong. Just tell the truth.

  2. Soleimani has declared war on the United States. A defensive war is obligatory for every real citizen.

    President Donald Trump represents every one of his constituents, all citizens, incuding Nancy Pelosi. Make America Great Again is good.

    Abortion is a preemptive war against overpopulation. Abortion destroys an innocent person deprived of his due process. Overpopulation is a lie. The death of an innocent person by the state is murder. Murder is only justified by self-defense, imminent self-defense. Never in the planning stage.

    Blackmailing “liberal” senators to get them to support nomination of a conservative Supreme Court Justice;
    If the “blackmail” has any truth behind it , it is a warning. The conservative Supreme Court Justice will take care of the crime.

    Leaking a false report about a conservative nominated for high administrative or judicial post.
    Lies come from liars. Nothing good comes from something bad
    We, the people owe our constitutional Posterity truth, Justice and the freedom to live their original innocence.
    Original sin is the propensity to commit actual sin. Original sin is like a broken immune system in nature. The Blessed Virgin Mary petitioned God for the grace to maintain her original innocence. Mary’s petition is granted. All sovereign persons from the womb ought to petition God for the grace to maintain our original innocence. At least we shall see where we have transgressed. And that is in itself a blessing. Know thyself.

  3. Catholic democrats aren’t the only Catholics confused by the principle of double effect, as is demonstrated every August when the morality of the atomic bombings of Hiroshima and Nagasaki are discussed.

  4. It should be nearly inconceivable that an orthodox Catholic would even consider voting for anyone other than Donald Trump. Donald Trump is our gift from God. He is indeed a stand-in for the man who thinks he’s Pope. (Just imagine the damage Hilary and Jorge Mario Bergolio could do together.)

    In the case of Trump the principle of double effect is not even operable. I do not see the “political reasons” cited above as rising that level.

    Donald Trump was clearly the right guy for President in 2016 and even more in 2020.

  5. “The morality of the atomic bombings of Hiroshima and Nagasaki”. If one American soldier was saved, the bombing are justified. This was Japan’s war. American did not start the war. Americans died in the war . The bomb ended the war.

  6. Is the following an example of the double effect principle? In WWII, my uncle Bob (RIP) was a machinist mate in USN Liberty ships in the Pacific theater. He was granted a liberty to attend his brother’s wedding. He was late returning and his Liberty, the USS Mount Hood, sailed without him. He was fined $50 and lost a stripe at the Captain’s Mast, like an Article 15 company punishment in the Army. Was the double effect how Mount Hood blew up in Manila Bay with all hands lost.

    People like Mark-who? disinter the Japan A bombs each year to politicize them so as to rationalize his major support for abortion and libel/slander anti-abortion Catholics.

    Uncle Bob (RIP) wanted to punch in the face everyone that spoke against the bombings. He would have, too.

  7. T. Shaw, I don’t think that was an example of the double effect principle, because I don’t think your uncle Bob (RIP) intended to miss the ship…so that wasn’t a deliberate action. Rather, it may be an example of God’s providence and special care for your uncle.

  8. Thank you for your comment, Grady Stuckman. I’m not sure what you mean by “voting scenario.” Are you referring to the item listed as “voting for appropriation bills that support both Planned Parenthood and Health Care for the poor?” If so, then one would have to think about proportionality. Conditions 1-4 could well be satisfied by an affirmative vote: the act of voting is itself morally neutral, as a legislator you intend for something good, money for health support for the poor; you personally don’t intend to support Planned Parenthood; and the support of Planned Parenthood is a “side effect,” not causal for the good effect. So what remains to be considered is the issue of proportionality. Is the financial support of Planned Parenthood so much an evil that it outweighs the good of health care money for the poor? Senator Bob Casey and other Catholic Democrat senators don’t think that’s the case. I disagree.

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