§ I. On fornication

493. Definition. - Fornication, if it is taken in a broad sense, is every illicit concubitus. - But strictly it is defined: Concubitus of an unmarried man with an unmarried woman from mutual consent. - Here "unmarried" is understood as one who is free from every bond of Matrimony, vow, or kinship in a prohibited degree.

Principles. - I. Fornication is utterly forbidden by natural right and by positive divine right, so that it can never be excused from grave sin. - This is clear: 1° From Sacred Scripture:¹ Neither fornicators shall possess the kingdom of God. Every fornicator or unclean person ... has no inheritance in the kingdom of Christ: 2° From reason; for, if fornication were permitted, men would generally withdraw from contracting Matrimony, and offspring received from fornication would be left without any education. But from this the subversion of social order would necessarily follow. St. Alphonsus adds:² "of itself it is against the right of nature to subject reason to the flesh, as happens in fornication on account of the delectation of the act; but in Matrimony, although the same delectation intervenes, God nevertheless by a special providence disposes that such disorder be absent."

II. To fornication, as to the same species, are referred concubinage and prostitution. - Concubinage properly so called is the habitual commerce of an unmarried man with an unmarried woman. It will be treated in n. 1438 sq. Prostitution is the state of a woman prostituted to many, at least to more than two. It is a most grave sin by reason of the disposition of soul, scandal, and harm of offspring, which is rarely born from prostitution, and, if ever it is born, is usually educated most badly.

The circumstance of concubinage or prostitution, although by reason of species it need not necessarily be declared in Confession, nevertheless per accidens it must ordinarily be explained for manifesting the state and genus of occasions, and must always be opened to the confessor when he asks.