Whether it is a mortal sin to have intercourse with a concubine?

❌ Objection 1 : It would seem that it is not a mortal sin to have intercourse with a concubine. For a lie is a greater sin than simple fornication: and a proof of this is that Juda, who did not abhor to commit fornication with Thamar, recoiled from telling a lie, saying (Gn. 38:23): "Surely she cannot charge us with a lie." But a lie is not always a mortal sin. Neither therefore is simple fornication.

❌ Objection 2 : Further, a deadly sin should be punished with death. But the Old Law did not punish with death intercourse with a concubine, save in a certain case (Dt. 22:25). Therefore it is not a deadly sin.

❌ Objection 3 : Further, according to Gregory (Moral. xxxiii, 12), the sins of the flesh are less blameworthy than spiritual sins. Now pride and covetousness, which are spiritual sins, are not always mortal sins. Therefore fornication, which is a sin of the flesh, is not always a mortal sin.

❌ Objection 4 : Further, where the incentive is greater the sin is less grievous, because he sins more who is overcome by a lighter temptation. But concupiscence is the greatest incentive to lust. Therefore since lustful actions are not always mortal sins, neither is simple fornication a mortal sin.