Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that simple fornication is not a mortal sin. For things that come under the same head would seem to be on a par with one another. Now fornication comes under the same head as things that are not mortal sins: for it is written (Acts 15:29): "That you abstain from things sacrificed to idols, and from blood, and from things strangled, and from fornication." But there is not mortal sin in these observances, according to 1 Tim. 4:4, "Nothing is rejected that is received with thanksgiving." Therefore fornication is not a mortal sin.

Objection 2: Further, no mortal sin is the matter of a Divine precept. But the Lord commanded (Osee 1:2): "Go take thee a wife of fornications, and have of her children of fornications." Therefore fornication is not a mortal sin.

Objection 3: Further, no mortal sin is mentioned in Holy Writ without disapprobation. Yet simple fornication is mentioned without disapprobation by Holy Writ in connection with the patriarchs. Thus we read (Gn. 16:4) that Abraham went in to his handmaid Agar; and further on (Gn. 30:5,9) that Jacob went in to Bala and Zelpha the handmaids of his wives; and again (Gn. 38:18) that Juda was with Thamar whom he thought to be a harlot. Therefore simple fornication is not a mortal sin.

Objection 4: Further, every mortal sin is contrary to charity. But simple fornication is not contrary to charity, neither as regards the love of God, since it is not a sin directly against. God, nor as regards the love of our neighbor, since thereby no one is injured. Therefore simple fornication is not a mortal sin.

Objection 5: Further, every mortal sin leads to eternal perdition. But simple fornication has not this result: because a gloss of Ambrose on 1 Tim. 4:8, "Godliness is profitable to all things," says: "The whole of Christian teaching is summed up in mercy and godliness: if a man conforms to this, even though he gives way to the inconstancy of the flesh, doubtless he will be punished, but he will not perish." Therefore simple fornication is not a mortal sin.

Objection 6: Further, Augustine says (De Bono Conjug. xvi) that "what food is to the well-being of the body, such is sexual intercourse to the welfare of the human race." But inordinate use of food is not always a mortal sin. Therefore neither is all inordinate sexual intercourse; and this would seem to apply especially to simple fornication, which is the least grievous of the aforesaid species.

On the contrary, It is written (Tob. 4:13): "Take heed to keep thyself . . . from all fornication, and beside thy wife never endure to know a crime." Now crime denotes a mortal sin. Therefore fornication and all intercourse with other than one's wife is a mortal sin.

Further, nothing but mortal sin debars a man from God's kingdom. But fornication debars him, as shown by the words of the Apostle (Gal. 5:21), who after mentioning fornication and certain other vices, adds: "They who do such things shall not obtain the kingdom of God." Therefore simple fornication is a mortal sin.

Further, it is written in the Decretals (XXII, qu. i, can. Praedicandum): "They should know that the same penance is to be enjoined for perjury as for adultery, fornication, and wilful murder and other criminal offenses." Therefore simple fornication is a criminal or mortal sin.

I answer that, Without any doubt we must hold simple fornication to be a mortal sin, notwithstanding that a gloss on Dt. 23:17, says: "This is a prohibition against going with whores, whose vileness is venial." For instead of "venial" it should be "venal," since such is the wanton's trade. In order to make this evident, we must take note that every sin committed directly against human life is a mortal sin. Now simple fornication implies an inordinateness that tends to injure the life of the offspring to be born of this union. For we find in all animals where the upbringing of the offspring needs care of both male and female, that these come together not indeterminately, but the male with a certain female, whether one or several; such is the case with all birds: while, on the other hand, among those animals, where the female alone suffices for the offspring's upbringing, the union is indeterminate, as in the case of dogs and like animals. Now it is evident that the upbringing of a human child requires not only the mother's care for his nourishment, but much more the care of his father as guide and guardian, and under whom he progresses in goods both internal and external. Hence human nature rebels against an indeterminate union of the sexes and demands that a man should be united to a determinate woman and should abide with her a long time or even for a whole lifetime. Hence it is that in the human race the male has a natural solicitude for the certainty of offspring, because on him devolves the upbringing of the child: and this certainly would cease if the union of sexes were indeterminate.

This union with a certain definite woman is called matrimony; which for the above reason is said to belong to the natural law. Since, however, the union of the sexes is directed to the common good of the whole human race, and common goods depend on the law for their determination, as stated above (1.2, Question 90, Article 2), it follows that this union of man and woman, which is called matrimony, is determined by some law. What this determination is for us will be stated in the Third Part of this work (XP, Question 50, seqq.), where we shall treat of the sacrament of matrimony. Wherefore, since fornication is an indeterminate union of the sexes, as something incompatible with matrimony, it is opposed to the good of the child's upbringing, and consequently it is a mortal sin.

Nor does it matter if a man having knowledge of a woman by fornication, make sufficient provision for the upbringing of the child: because a matter that comes under the determination of the law is judged according to what happens in general, and not according to what may happen in a particular case.

Reply to Objection 1: Fornication is reckoned in conjunction with these things, not as being on a par with them in sinfulness, but because the matters mentioned there were equally liable to cause dispute between Jews and Gentiles, and thus prevent them from agreeing unanimously. For among the Gentiles, fornication was not deemed unlawful, on account of the corruption of natural reason: whereas the Jews, taught by the Divine law, considered it to be unlawful. The other things mentioned were loathsome to the Jews through custom introduced by the law into their daily life. Hence the Apostles forbade these things to the Gentiles, not as though they were unlawful in themselves, but because they were loathsome to the Jews, as stated above (1.2, Question 103, Article 4, ad 3).

Reply to Objection 2: Fornication is said to be a sin, because it is contrary to right reason. Now man's reason is right, in so far as it is ruled by the Divine Will, the first and supreme rule. Wherefore that which a man does by God's will and in obedience to His command, is not contrary to right reason, though it may seem contrary to the general order of reason: even so, that which is done miraculously by the Divine power is not contrary to nature, though it be contrary to the usual course of nature. Therefore just as Abraham did not sin in being willing to slay his innocent son, because he obeyed God, although considered in itself it was contrary to right human reason in general, so, too, Osee sinned not in committing fornication by God's command. Nor should such a copulation be strictly called fornication, though it be so called in reference to the general course of things. Hence Augustine says (Confess. iii, 8): "When God commands a thing to be done against the customs or agreement of any people, though it were never done by them heretofore, it is to be done"; and afterwards he adds: "For as among the powers of human society, the greater authority is obeyed in preference to the lesser, so must God in preference to all."

Reply to Objection 3: Abraham and Jacob went in to their handmaidens with no purpose of fornication, as we shall show further on when we treat of matrimony (XP, Question 65, Article 5, ad 2). As to Juda there is no need to excuse him, for he also caused Joseph to be sold.

Reply to Objection 4: Simple fornication is contrary to the love of our neighbor, because it is opposed to the good of the child to be born, as we have shown, since it is an act of generation accomplished in a manner disadvantageous to the future child.

Reply to Objection 5: A person, who, while given to works of piety, yields to the inconstancy of the flesh, is freed from eternal loss, in so far as these works dispose him to receive the grace to repent, and because by such works he makes satisfaction for his past inconstancy; but not so as to be freed by pious works, if he persist in carnal inconstancy impenitent until death.

Reply to Objection 6: One copulation may result in the begetting of a man, wherefore inordinate copulation, which hinders the good of the future child, is a mortal sin as to the very genus of the act, and not only as to the inordinateness of concupiscence. On the other hand, one meal does not hinder the good of a man's whole life, wherefore the act of gluttony is not a mortal sin by reason of its genus. It would, however, be a mortal sin, if a man were knowingly to partake of a food which would alter the whole condition of his life, as was the case with Adam.

Nor is it true that fornication is the least of the sins comprised under lust, for the marriage act that is done out of sensuous pleasure is a lesser sin.

Articulus 2

Argumentum 1

Ad secundum sic proceditur. Videtur quod fornicatio simplex non sit peccatum mortale. Ea enim quae simul connumerantur, videntur esse unius rationis. Sed fornicatio connumeratur quibusdam quae non sunt peccata mortalia, dicitur enim Act. XV, abstineatis vos ab immolatis simulacrorum, et sanguine et suffocato, et fornicatione; illorum autem usus non est peccatum mortale, secundum illud I ad Tim. IV, nihil reiiciendum quod cum gratiarum actione percipitur.

Ergo fornicatio non est peccatum mortale.

Argumentum 2

Praeterea, nullum peccatum mortale cadit sub praecepto divino.

Sed Osee I praecipitur a domino, vade, sume tibi uxorem fornicationum, et fac filios fornicationum.

Ergo fornicatio non est peccatum mortale.

Argumentum 3

Praeterea, nullum peccatum mortale in Scriptura sacra absque reprehensione commemoratur. Sed fornicatio simplex commemoratur in Scriptura in antiquis patribus sine reprehensione, sicut legitur Gen. XVI de Abraham quod accessit ad Agar, ancillam suam; et infra, XXX, legitur de Iacob quod accessit ad ancillas uxorum suarum Balam et zelpham; et infra, XXXVIII, legitur quod Iudas accessit ad thamar, quam aestimavit meretricem.

Ergo fornicatio simplex non est peccatum mortale.

Argumentum 4

Praeterea, omne peccatum mortale contrariatur caritati.

Sed fornicatio simplex non contrariatur caritati, neque quantum ad dilectionem dei, quia non est directe peccatum contra deum; nec etiam quantum ad dilectionem proximi, quia per hoc homo nulli homini facit iniuriam.

Ergo fornicatio simplex non est peccatum mortale.

Argumentum 5

Praeterea, omne peccatum mortale ducit in perditionem aeternam.

Hoc autem non facit fornicatio simplex, quia super illud I ad Tim. IV, pietas ad omnia utilis est, dicit Glossa Ambrosii, omnis summa disciplinae christianae in misericordia et pietate est. Quam aliquis sequens, si lubricum carnis patitur, sine dubio vapulabit, sed non peribit.

Ergo fornicatio simplex non est peccatum mortale.

Argumentum 6

Praeterea, sicut Augustinus dicit, in libro de bon. Coniug., quod est cibus ad salutem corporis, hoc est concubitus ad salutem generis.

Sed non omnis inordinatus usus ciborum est peccatum mortale. Ergo nec omnis inordinatus concubitus. Quod maxime videtur de fornicatione simplici, quae minima est inter species enumeratas.

Sed Contra 1

Sed contra est quod dicitur tobiae IV, attende tibi ab omni fornicatione, et praeter uxorem tuam, non patiaris crimen scire.

Crimen autem importat peccatum mortale. Ergo fornicatio, et omnis concubitus qui est praeter uxorem, est peccatum mortale.

Sed Contra 2

Praeterea, nihil excludit a regno dei nisi peccatum mortale.

Fornicatio autem excludit, ut patet per apostolum, Galat. V, ubi, praemissa fornicatione, et quibusdam aliis vitiis, subdit, qui talia agunt, regnum dei non possidebunt.

Ergo fornicatio simplex est peccatum mortale.

Sed Contra 3

Praeterea, in decretis dicitur, XXII caus., qu. I, nosse debent talem de periurio poenitentiam imponi debere qualem de adulterio et fornicatione, et de homicidio sponte commisso, et de ceteris criminalibus vitiis.

Ergo fornicatio simplex est peccatum criminale, sive mortale.

Corpus

Respondeo dicendum quod absque omni dubio tenendum est quod fornicatio simplex sit peccatum mortale, non obstante quod Deut. XXIII, super illud, non erit meretrix etc., dicit Glossa, ad eas prohibet accedere quarum est venialis turpitudo.

Non enim debet dici venialis, sed venalis, quod est proprium meretricum.

Ad huius autem evidentiam, considerandum est quod peccatum mortale est omne peccatum quod committitur directe contra vitam hominis. Fornicatio autem simplex importat inordinationem quae vergit in nocumentum vitae eius qui est ex tali concubitu nasciturus. Videmus enim in omnibus animalibus in quibus ad educationem prolis requiritur cura maris et feminae, quod in eis non est vagus concubitus, sed maris ad certam feminam, unam vel plures, sicut patet in omnibus avibus. Secus autem est in animalibus in quibus sola femina sufficit ad educationem fetus in quibus est vagus concubitus, ut patet in canibus et aliis huiusmodi animalibus. Manifestum est autem quod ad educationem hominis non solum requiritur cura matris, a qua nutritur, sed multo magis cura patris, a quo est instruendus et defendendus, et in bonis tam interioribus quam exterioribus promovendus. Et ideo contra naturam hominis est quod utatur vago concubitu, sed oportet quod sit maris ad determinatam feminam, cum qua permaneat, non per modicum tempus, sed diu, vel etiam per totam vitam. Et inde est quod naturaliter est maribus in specie humana sollicitudo de certitudine prolis, quia eis imminet educatio prolis. Haec autem certitudo tolleretur si esset vagus concubitus. Haec autem determinatio certae feminae matrimonium vocatur. Et ideo dicitur esse de iure naturali. Sed quia concubitus ordinatur ad bonum commune totius humani generis; bona autem communia cadunt sub determinatione legis, ut supra habitum est, consequens est quod ista coniunctio maris ad feminam, quae matrimonium dicitur, lege aliqua determinetur.

Qualiter autem sit apud nos determinatum, in tertia parte huius operis agetur, cum de matrimonii sacramento tractabitur.

Unde, cum fornicatio sit concubitus vagus, utpote praeter matrimonium existens, est contra bonum prolis educandae. Et ideo est peccatum mortale. Nec obstat si aliquis fornicando aliquam cognoscens, sufficienter provideat proli de educatione. Quia id quod cadit sub legis determinatione, iudicatur secundum id quod communiter accidit, et non secundum id quod in aliquo casu potest accidere.

Ad 1

Ad primum ergo dicendum quod fornicatio illis connumeratur, non quia habeat eandem rationem culpae cum aliis, sed quantum ad hoc, quod ex his quae ibi ponuntur similiter poterat dissidium generari inter Iudaeos et gentiles, et eorum unanimis consensus impediri. Quia apud gentiles fornicatio simplex non reputabatur illicita, propter corruptionem naturalis rationis, Iudaei autem, ex lege divina instructi, eam illicitam reputabant. Alia vero quae ibi ponuntur, Iudaei abominabantur propter consuetudinem legalis conversationis. Unde apostoli ea gentilibus interdixerunt, non quasi secundum se illicita, sed quasi Iudaeis abominabilia, ut etiam supra dictum est.

Ad 2

Ad secundum dicendum quod fornicatio dicitur esse peccatum, inquantum est contra rationem rectam. Ratio autem hominis recta est secundum quod regulatur voluntate divina, quae est prima et summa regula. Et ideo quod homo facit ex voluntate dei, eius praecepto obediens, non est contra rationem rectam, quamvis videatur esse contra communem ordinem rationis, sicut etiam non est contra naturam quod miraculose fit virtute divina, quamvis sit contra communem cursum naturae. Et ideo, sicut Abraham non peccavit filium innocentem volendo occidere, propter hoc quod obedivit deo, quamvis hoc, secundum se consideratum, sit communiter contra rectitudinem rationis humanae; ita etiam Osee non peccavit fornicando ex praecepto divino. Nec talis concubitus proprie fornicatio debet dici, quamvis fornicatio nominetur referendo ad cursum communem.

Unde Augustinus dicit, III confess., cum deus aliquid contra morem aut pactum quorumlibet iubet, etsi nunquam ibi factum est, faciendum est.

Et postea subdit, sicut enim in potestatibus societatis humanae maior potestas minori ad obediendum praeponitur, ita deus omnibus.

Ad 3

Ad tertium dicendum quod Abraham et Iacob ad ancillas accesserunt non quasi fornicario concubitu, ut infra patebit, cum de matrimonio agetur.

Iudam autem non est necessarium a peccato excusare, qui etiam auctor fuit venditionis ioseph.

Ad 4

Ad quartum dicendum quod fornicatio simplex contrariatur dilectioni proximi quantum ad hoc, quod repugnat bono prolis nasciturae, ut ostensum est, dum scilicet dat operam generationi non secundum quod convenit proli nasciturae.

Ad 5

Ad quintum dicendum quod per opera pietatis ille qui lubricum carnis patitur liberatur a perditione aeterna, inquantum per huiusmodi opera disponitur ad hoc quod gratiam consequatur per quam poeniteat, et inquantum per huiusmodi opera satisfacit de lubrico carnis commisso. Non autem ita quod, si in lubrico carnis perseveret impoenitens usque ad mortem, per pietatis opera liberetur.

Ad 6

Ad sextum dicendum quod ex uno concubitu potest unus homo generari. Et ideo inordinatio concubitus, quae impedit bonum prolis nasciturae, ex ipso genere actus est peccatum mortale, et non solum ex inordinatione concupiscentiae. Ex una autem comestione non impeditur bonum totius vitae unius hominis, et ideo actus gulae ex suo genere non est peccatum mortale. Esset tamen si quis scienter cibum comederet qui totam conditionem vitae eius immutaret, sicut patet de Adam. Nec tamen fornicatio est minimum peccatorum quae sub luxuria continentur. Minus enim est concubitus cum uxore qui fit ex libidine.