The Double Effect Principle and Abortion:
A Primer for Catholic Legislators*


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″



Politicians use all sorts of rationalizations to justify expedient positions. For example, Mario Cuomo (the intelligent one, Cuomo pere) said in an address at Notre Dame University (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.

This argument is, to put it mildly, disingenuous.  Moral principles are supposed to be universal. Had Mario Cuomo opposed forced Sunday attendance at Mass, then his argument would be appropriate.  Had he been an Orthodox Jew, but opposed to the prohibition of driving on Saturday…OK.  But the sanctity of life is a universal moral precept.   Would one 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 the need for 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.

Senator Bob Casey, Jr., 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 does one 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.


The Stanford Encyclopedia of Philosophy gives a lucid, detailed account, as does Fr. Faulkner’s blog post, linked below in the image caption.  Go to the image below 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.
Diagram of Double Effect, from Fr. Joseph Faulkner’s blog, “The Pastor talks too fast”

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

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.   (One assumes that  both the woman and foetus would die if the procedure would not be carried out .)

Note how following example is different: 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.


In the original version of this article, Grady Stuckman (“Clarifying Catholicism”) gave a  comment that might be discussed at greater length.  Namely, how might a Catholic legislator apply the double effect principle to voting for an appropriations bill that gave money both to Planned Parenthood and to health provisions for needy people.

Recall that Senator Bob Casey, Jr. and some other Catholic Democratic Senators have voted for appropriation bills that give financial support to Planned Parenthood.  They justify such a vote by arguing that the money supports women’s health programs.   Does this good effect justify the bad effect of abortions carried out by Planned Parenthood?  Let’s examine  the five requirements listed above.

  1.  The act of voting is in itself not evil; it’s either neutral or good, so that requirement is satisfied.
  2.  Presumably  Senator Casey and the other senators do not intend that the money given to Planned Parenthood be used for abortions. Accordingly, the requirement for no evil intent is  satisfied. But, do  the senators really consider this consequence of their vote?
  3. The presumed good effect is that the appropriation will be used for beneficial health care (mammograms, etc.)  How much “good” health care does Planned Parenthood carry out that is not already available at hospitals and clinics?
  4. If money is used by Planned Parenthood for abortions, that use is a “side effect,” it is not causal for the “good” programs carried out by Planned Parenthood.
  5. Proportionality: Senator Casey and his Democratic colleagues say that the effect of abortions carried out by Planned Parenthood is not bad enough to outweigh the good done by the organization’s other health care programs. Clearly this assessment is a rationalization, contrary to Catholic teaching.

One can conclude  that the required conditions 1-4 might (with some loose interpretation) be satisfied by such a vote.   But, should any faithful Catholic believe that the proportionality condition is met?


*This article is adapted from one by Bob Kurland in The American Catholic. (with permission)

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2 thoughts on “The Double Effect Principle and Abortion: <br> A Primer for Catholic Legislators*”

  1. Good article and comment. Very logical and well said. Unfortunately, the innate thirst for power and approval of many (most?) of our legislators at all levels relegate logic and morality to a subordinate level. It is said that we get the government that we choose and deserve. Possibly so, but it is most unfortunate that the innocent are dragged along in this process.

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

    Absolutely Balderdash! If Senator Bob Casey really wants to support women’s health, then he (and other mis-guided Catholic Democrats) should defund Planned Parenthood completely and put the Federal monies into FQHC’s, RHC’s and LA’s. There are about 20 of these true women and FAMILY health centers to every 1 Planned Parenthood centers. In 2018 Planned Parenthood completed 332,757 abortion procedures. Shameful.

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