Thus, we here find adultery understood as always and necessarily wrongful, yet not defined in terms of its wrongfulness. It is not specified as wrongful or inordinate or unchaste sex by a married person outside marriage—as sex without proportionate reason. It is defined as sex by a married person outside marriage. The specification needs interpretation and elaboration, since there are questions to be answered about who is indeed married. Christian tradition, as Paul makes clear (1 Corinthians 7), has never treated these questions as simple. But where, as in most cases of adultery, there is no doubt that the one party, if married, is not married to the other, then the Lord's precept applies exceptionlessly, whatever the (other) circumstances.
The same absoluteness of the properly (but still nonevaluatively) specified norm excluding adultery is found in the constant Christian tradition, from the beginning, against abortion, suicide, fornication, homosexual sex, and blasphemy and disclaimer of the faith. The tradition is massively solid. It has cogent grounds, in faith and reason, as we shall see. And it is witnessed to by martyrdom willingly suffered rather than consent to what the martyr takes to be an act of such a description. The oppressors, the tempters, the crowd, all persuasively present the act as an evil lesser than death, disgrace, ruin for the martyr's family; a Thomas More or a Maria Goretti judges the act to be wrong per se and in se and, precisely because immoral, to be an evil greater than any amount of evil set in train by refusing to choose such an act. The church judges them to be saints, along with the many unnamed martyrs.
(John Finnis, Moral Absolutes: Tradition, Revision, and Truth [Washington, DC: The Catholic University of America Press, 1991], 8-9 [italics in original; footnotes omitted])
Note from KBJ: Fiat justitia, ruat cœlum.
Keith Burgess-Jackson, J.D., Ph.D. 