The difference between sin and law


I know there are things that the Church/CA teach are both immoral/sins and should be ILLEGAL. Things like gay “marriage”, abortion, euthanasia etc. However, there are things that the Church/CA teach that are a bit confusing. For example, I know as Catholics we believe that things such as homosexual/pre-marital/polygamous intercourse, masturbation, contraception, pornography etc. are sins/immoral but I don’t know if that means that we should OUTLAW them. Where do we draw the line between “This is both a sin and should be outlawed” and “This is a sin but should still be legal to do”?


I think the general rule is that something should be illegal if it has a direct, negative impact on society as a whole.

Whether or not that’s true for a particular sin can be a matter of prudential judgment, but it many cases, such as pornography and abortion, the negative impact to the person and society is readily apparent.


In addition to what ProdglArchitect said, we have to look realistically at whether a law could be enforced. It would be virtually impossible to enforce a law against masturbation, or against sex outside marriage, without having Big Brother-style hidden cameras in everybody’s home, watching people’s private behavior. Such sinful behaviors are also so widespread, it would be a huge burden on society to be arresting or fining someone every time they engaged in a sinful sexual act. The Church realistically understands legal regulation of these behaviors is not going to work in this society and calls on each person to self-regulate.


First, there can be no law affirmatively commanding sin or (participation in another’s sin, etc.) encouraging, affirming, or sanctioning sin as a good or proper right. However, sin can and often should be tolerated.

It all comes down to what best serves the common good.

Pope Leo XIII, Libertas

  1. [The Church] does not forbid public authority to tolerate what is at variance with truth and justice, for the sake of avoiding some greater evil, or of obtaining or preserving some greater good. God Himself in His providence, though infinitely good and powerful, permits evil to exist in the world, partly that greater good may not be impeded, and partly that greater evil may not ensue. In the government of States it is not forbidden to imitate the Ruler of the world; and, as the authority of man is powerless to prevent every evil, it has (as St. Augustine says) to overlook and leave unpunished many things which are punished, and rightly, by Divine Providence.(10) But if, in such circumstances, for the sake of the common good (and this is the only legitimate reason), human law may or even should tolerate evil, it may not and should not approve or desire evil for its own sake; for evil of itself, being a privation of good, is opposed to the common welfare which every legislator is bound to desire and defend to the best of his ability. In this, human law must endeavor to imitate God, who, as St. Thomas teaches, in allowing evil to exist in the world, “neither wills evil to be done, nor wills it not to be done, but wills only to permit it to be done; and this is good.”(11) This saying of the Angelic Doctor contains briefly the whole doctrine of the permission of evil.

  2. But, to judge aright, we must acknowledge that, the more a State is driven to tolerate evil, the further is it from perfection; and that the tolerance of evil which is dictated by political prudence should be strictly confined to the limits which its justifying cause, the public welfare, requires. Wherefore, if such tolerance would be injurious to the public welfare, and entail greater evils on the State, it would not be lawful; for in such case the motive of good is wanting.


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