Aquinas on Unnatural Sex
Thomas Aquinas (1224/25-75) is commonly regarded as the greatest Western philosopher of the thirteenth century. In a series of works he addressed all the current issues of theology and philosophy, and in particular the problem Christian thinkers had in dealing with the arrival of good editions of the works of Aristotle in the West.
Aquinas was both intensely productive and quite flexible in his approaches. [On occasion he reportedly was able to write, via dictation, two ore more works at a time]. Because of the formidable extent of his works, it is often his two great summas to which we turn to find out what he thought. This is not always wise. The summas were consciously written as compendia, and Aquinas addressed a number of theoretical issues in smaller subject specific treatises. Moreover, many of the common questions in thirteenth centuiy academic discussion were based on questions from the basic Theologiael textbook, Peter Lombard's Four Books of Sentences, and it is to Aquinas' commentaries on these that one should turn for his discussion of issues such as women clergy, or the moment of consecration.
The summas [the Summa Theologiae and the Summa Contra Gentiles] are, however, useful. Echoing the disputation methods of university teaching, the Summa Theologiae
presents a summation of Aquinas' opinions on issues from the existence of God, to the sacremental system, to basic moral rules.
The selection here addresses Aquinas discussion of sex and sexuality. It shows both his typical methods - his willingness to face objections openly, his use of authorities, and his use of logic - as well as the effort to construct the intractable realities of human experience into a structured and analyzable form.
Extracts from Summa Theologiae II-II, question 154
The following issues are addressed by Aquinas in these selections:-
Summa Theologica II-II, 154, 11:Whether the unnatural vice is a species of lust?
Summa Theologiae II-II, 154, 12: Whether the unnatural vice is the greatest sin among the species of lust?
Aquinas' discussion of sexual morality in general [which includes fornication, incest, and rape], is available in a separate document, Aquinas on Sex
Summa Theologica II-II, 154, 11
Whether the unnatural vice is a species of lust?
Objection 1. It would seem that the unnatural vice is not a species of lust.
For no mention of the vice against nature is made in the enumeration
given above (1, Objection 1). Therefore it is not a species of lust.
Objection 2. Further, lust is contrary to virtue; and so it is comprised under
vice. But the unnatural vice is comprised not under vice, but under
bestiality, according to the Philosopher (Ethic. vii, 5). Therefore the
unnatural vice is not a species of lust.
Objection 3. Further, lust regards acts directed to human generation, as
stated above (153, 2): Whereas the unnatural vice concerns acts
from which generation cannot follow. Therefore the unnatural vice is not
a species of lust.
On the contrary, It is reckoned together with the other species of lust
(2 Cor. 12:21) where we read: "And have not done penance for the
uncleanness, and fornication, and lasciviousness," where a gloss says:
"Lasciviousness, i.e., unnatural lust."
I answer that, As stated above (A6,9) wherever there occurs a special
kind of deformity whereby the venereal act is rendered unbecoming, there
is a determinate species of lust. This may occur in two ways: First,
through being contrary to right reason, and this is common to all
lustful vices; secondly, because, in addition, it is contrary to the
natural order of the venereal act as becoming to the human race: and this
is called "the unnatural vice." This may happen in several ways. First,
by procuring pollution, without any copulation, for the sake of venereal
pleasure: this pertains to the sin of "uncleanness" which some call
"effeminacy." Secondly, by copulation with a thing of undue species, and
this is called "bestiality." Thirdly, by copulation with an undue sex,
male with male, or female with female, as the Apostle states (Rm. 1:27):
and this is called the "vice of sodomy." Fourthly, by not observing the
natural manner of copulation, either as to undue means, or as to other
monstrous and bestial manners of copulation.
Reply to Objection 1. There we enumerated the species of lust that are not
contrary to human nature: wherefore the unnatural vice was omitted.
Reply to Objection 2. Bestiality differs from vice, for the latter is opposed to
human virtue by a certain excess in the same matter as the virtue, and
therefore is reducible to the same genus.
Reply to Objection 3. The lustful man intends not human generation but venereal
pleasures. It is possible to have this without those acts from which
human generation follows: and it is that which is sought in the unnatural
Summa Theologica II-II, 154, 12
Whether the unnatural vice is the greatest sin among the species of lust?
Objection 1. It would seem that the unnatural vice is not the greatest sin
among the species of lust. For the more a sin is contrary to charity the
graver it is. Now adultery, seduction and rape which are injurious to our
neighbor are seemingly more contrary to the love of our neighbor, than
unnatural sins, by which no other person is injured. Therefore the
unnatural sin is not the greatest among the species of lust.
Objection 2. Further, sins committed against God would seem to be the most
grievous. Now sacrilege is committed directly against God, since it is
injurious to the Divine worship. Therefore sacrilege is a graver sin than
the unnatural vice.
Objection 3. Further, seemingly, a sin is all the more grievous according as
we owe a greater love to the person against whom that sin is committed.
Now the order of charity requires that a man love more those persons who
are united to him---and such are those whom he defiles by incest---than
persons who are not connected with him, and whom in certain cases he
defiles by the unnatural vice. Therefore incest is a graver sin than the
Objection 4. Further, if the unnatural vice is most grievous, the more it is
against nature the graver it would seem to be. Now the sin of
uncleanness or effeminacy would seem to be most contrary to nature, since
it would seem especially in accord with nature that agent and patient
should be distinct from one another. Hence it would follow that
uncleanness is the gravest of unnatural vices. But this is not true.
Therefore unnatural vices are not the most grievous among sins of lust.
On the contrary, Augustine says (De adult. conjug. [The quotation is
from Cap. Adulterii xxxii, qu. 7. Cf. Augustine, De Bono Conjugali,
viii.]) that "of all these," namely the sins belonging to lust, "that
which is against nature is the worst."
I answer that, In every genus, worst of all is the corruption of the
principle on which the rest depend. Now the principles of reason are
those things that are according to nature, because reason presupposes
things as determined by nature, before disposing of other things
according as it is fitting. This may be observed both in speculative and
in practical matters. Wherefore just as in speculative matters the most
grievous and shameful error is that which is about things the knowledge
of which is naturally bestowed on man, so in matters of action it is most
grave and shameful to act against things as determined by nature.
Therefore, since by the unnatural vices man transgresses that which has
been determined by nature with regard to the use of venereal actions, it
follows that in this matter this sin is gravest of all. After it comes
incest, which, as stated above (09), is contrary to the natural respect
which we owe persons related to us.
With regard to the other species of lust they imply a transgression
merely of that which is determined by right reason, on the
presupposition, however, of natural principles. Now it is more against
reason to make use of the venereal act not only with prejudice to the
future offspring, but also so as to injure another person besides.
Wherefore simple fornication, which is committed without injustice to
another person, is the least grave among the species of lust. Then, it is
a greater injustice to have intercourse with a woman who is subject to
another's authority as regards the act of generation, than as regards
merely her guardianship. Wherefore adultery is more grievous than
seduction. And both of these are aggravated by the use of violence. Hence
rape of a virgin is graver than seduction, and rape of a wife than
adultery. And all these are aggravated by coming under the head of
sacrilege, as stated above (10, ad 2).
Reply to Objection 1. Just as the ordering of right reason proceeds from man, so
the order of nature is from God Himself: wherefore in sins contrary to
nature, whereby the very order of nature is violated, an injury is done
to God, the Author of nature. Hence Augustine says (Confess. iii, 8):
"Those foul offenses that are against nature should be everywhere and at
all times detested and punished, such as were those of the people of
Sodom, which should all nations commit, they should all stand guilty of
the same crime, by the law of God which hath not so made men that they
should so abuse one another. For even that very intercourse which should
be between God and us is violated, when that same nature, of which He is
the Author, is polluted by the perversity of lust."
Reply to Objection 2. Vices against nature are also against God, as stated above
(ad 1), and are so much more grievous than the depravity of sacrilege, as
the order impressed on human nature is prior to and more firm than any
subsequently established order.
Reply to Objection 3. The nature of the species is more intimately united to each
individual, than any other individual is. Wherefore sins against the
specific nature are more grievous.
Reply to Objection 4. Gravity of a sin depends more on the abuse of a thing than
on the omission of the right use. Wherefore among sins against nature,
the lowest place belongs to the sin of uncleanness, which consists in the
mere omission of copulation with another. While the most grievous is the
sin of bestiality, because use of the due species is not observed. Hence
a gloss on Gn. 37:2, "He accused his brethren of a most wicked crime,"
says that "they copulated with cattle." After this comes the sin of
sodomy, because use of the right sex is not observed. Lastly comes the
sin of not observing the right manner of copulation, which is more
grievous if the abuse regards the "vas" than if it affects the manner of
copulation in respect of other circumstances.
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(c)Paul Halsall Mar 1996