The Principle of Double Effect and Intrinsic Evil

Double Effect

The principle of double effect considers the moral situation where a knowingly chosen act has two substantial effects (consequences), one good and one bad. The principle of double effect justifies the overall act (all three fonts of morality) only when certain criteria are met. But in all cases, the principle of double effect is not an exception to the magisterial teaching on the three fonts of morality. Rather, it is an application of the three fonts to a particular type of act, one with a double effect.

The Magisterium teaches that for any act to be moral, all three fonts of morality must be good: (1) intended end, (2) moral object, (3) circumstances. Catechism of the Catholic Church: “A morally good act requires the goodness of the object, of the end, and of the circumstances together.” [CCC 1755].

So it is impossible for an act to be justified by the principle of double effect, unless all three fonts of morality are good. Any one bad font makes the overall act objectively a sin. And this is why every sound explanation of the principle of double effect specifies that the act itself cannot be intrinsically evil. The principle of double effect never justifies an intrinsically evil act.

The usual expression of the principle of double effect (for example here: Principle of Double Effect) lists a set of criteria which must be met for the act to be moral. But we can restate that same teaching in terms of the three fonts of morality:

1. Intended end
All that is intended by the person must be good. For an act with two effects, one good and one bad, the person cannot intend the bad effect as an end. The good effect can be intended, along with any other end that is good.

2. Moral object
The chosen act cannot be intrinsically evil. In other words, the moral object of the knowingly chosen act must be good. If the act has more than one moral object, then all these objects must be good. One or more bad moral objects makes the act inherently immoral and therefore always wrong to choose.

3. Circumstances
The usual criteria used to evaluate an act under the principle of double effect are mainly concerned with the consequences in the font of circumstances. For all moral acts, the reasonably anticipated bad consequences must not morally outweigh the reasonably anticipated good consequences. And this evaluation must take into account considerations such as whether a consequence is more or less distant from the act (giving it differing moral weight), and whether the good consequences could be obtained by a different act without any substantial bad consequences.


Can the good effect sometimes be obtained by means of the bad effect? The usual statement of the principle of double effect prohibits this relationship. But in my view, as long as all three fonts of morality are good, there is no absolute prohibition against such a relation between the two effects.

For example, a physician amputates a limb to save a life. All Catholic ethicists agree his act is moral, given only good in the intention and no other treatment that will do less harm. Yet the bad effect, loss of a limb, is the means to the good effect, the preservation of life.

Can the bad effect sometimes be intended? The physician intends to save a life. In some sense, he does intend to amputate a limb. But he intends the amputation only as a means. The bad effect can be intended as a means to the good effect when it is not morally bad, but only a type of physical evil (harm or disorder). It is never moral to intend physical evil as an end, nor to intend moral evil as an end or a means.

When is the bad effect not permissible as a means to the good effect? When the bad effect is also a bad end in the moral object of the act, making it morally bad. Any evil in the moral object makes the act intrinsically evil and therefore always immoral. The principle of double effect NEVER justifies an intrinsically evil act.

A Perversion of This Principle

Some Catholic authors have decided to turn the principle of double effect upside-down. They claim that we can use the principle of double effect to determine if an act is intrinsically evil. Gone is the first condition that the act must not be intrinsically evil. What we are left with is a claim that if all the other conditions of the principle of double effect are met, then the act cannot be intrinsically evil.

Essentially, what this perverse analysis of acts with double effects does is morally evaluate only the intention and the circumstances of the act, ignoring the moral object. Then if those two fonts are good, the act is said to be justified by the principle of double effect, despite being the very same concrete act condemned by the Church as intrinsically evil. When confronted by the teaching of the Magisterium that such an act is intrinsically evil, the claim is made that with this particular intention, in these circumstances, the act is no longer intrinsically evil and no longer properly defined as abortion or contraception or some other grave sin.

What happens to the font called moral object in such a perverse application of the principle of double effect? It is said to be determined by the intention of the human person, not by the ordering of the chosen act toward its proximate end. The three fonts of morality taught be the Church becomes two fonts: (1) intention, (2) intention again, (3) circumstances. The principle of double effect is thereby used to redefine the moral object and the act, with the result that intrinsically evil acts are considered good and moral.

Such a claim is entirely incompatible with the teaching of the Magisterium on intrinsically evil acts, and with the traditional teaching of moral theology on the principle of double effect. And yet this claim is spreading among the faithful, as if it were the teaching of the Church.

{5:17} Do not think that I have come to loosen the law or the prophets. I have not come to loosen, but to fulfill.
{5:18} Amen I say to you, certainly, until heaven and earth pass away, not one iota, not one dot shall pass away from the law, until all is done.
{5:19} Therefore, whoever will have loosened one of the least of these commandments, and have taught men so, shall be called the least in the kingdom of heaven. But whoever will have done and taught these, such a one shall be called great in the kingdom of heaven.
{5:20} For I say to you, that unless your justice has surpassed that of the scribes and the Pharisees you shall not enter into the kingdom of heaven.

Ronald L. Conte Jr.
Roman Catholic theologian and
translator of the Catholic Public Domain Version of the Bible.

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2 Responses to The Principle of Double Effect and Intrinsic Evil

  1. Francisco says:

    What about when the anticipated good and the bad effects are very narrow?

    For example, a person anticipates (or thinks) a good effect but only by a tiny margin over a possible bad effect? So, this is a matter of degree. Should the person refrain from doing this particular act because the anticipated good and bad effects are so close in this case?

    Good intention, good moral object, but considers good consequences only by a very tiny margin over bad consequences.

    • Ron Conte says:

      Even if the good effects only equal the bad effects, the act is morally permissible because the benefits morally cancel out the detriments, and the intention and act itself are good. Perhaps the person “should” choose an act with greater benefits, but he is nor morally required to avoid the permissible act.

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