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Rachel wrote:

Hi, guys —

My apologies if I misunderstand the doctrine of double effect, but I was wondering:

  • Whether, under that principle, the use of barrier contraception methods such as condoms would be morally permissible if they were used exclusively:

    • as a way of preventing the spread of (STDs) Sexually Transmitted Diseases, and
    • the contraceptive element was only an undesirable side effect?

  • If that was the case, would it be justifiable to use prophylaxis only if the user was having sex with someone with a confirmed infection?
  • Would it be acceptable to use them to prevent the spread of any sexually transmitted infections or only those which are potentially fatal?


  { Under the doctrine of double effect would using contraception methods be OK to prevent STDs? }

Fr. Tad Pacholczyk replied:

Hello Rachel,

Mike forwarded your question to me from

Briefly, the principle of double effect cannot be applied to the situation you mention, because the requirements of the principle are not satisfied.

First, the principle requires a single action be carried out which has two effects. In the situation you mention, two separate actions are really involved:

  1. action one: rolling on the condom
  2. action two: engaging in intentionally rendered infecund genital sexual activity

Action two, you will note, does not have a double effect, one good and one bad. Rather, it is, in and of itself, a disordered or bad act. The problem with the approach outlined in your e-mail is that it involves consenting to acts that are fundamentally non-marital in nature. The old moralists had a Latin phrase that described the type of act, as one involving a vas indebitum, meaning, literally, an undue vessel. Intercourse with deposition into other than the woman's reproductive tract raises these fundamental moral concerns.

Hence, in the final analysis, one is freely deciding to engage in a disordered and evil act, that various goods may follow. One is choosing a disordered action, so as to bring about two putative goods:

  1. the inducing of experiences of mutual pleasure between spouses
  2. thwarting the transmission of a disease-causing agent during the action of inducing mutually pleasurable experiences between spouses

In conclusion, in terms of attempting to justify condom use as a prophylactic, action two mentioned above fails to satisfy the first requirement of the principle, namely, that the act itself be good or indifferent, and hence the principle cannot be applied.

Secondly, the posited action itself does not result in a double effect, but is rather an action that is properly identified, in itself, as intrinsically disordered.

Please see the following documents for further information on this important topic.

Thank you for your consultation question.


Fr. Tad
National Catholic Bioethics Center

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