Question Four: Concerning Lust Consummated against Nature

I. Lust against nature is so called because it altogether repugns the natural ordering or destination of the venereal act, while it impedes generation. There are four species of it distinct by object. For the genital act, in order that offspring may be conceived, requires four things: a. the concubitus of two; b. of different sex; c. of the same specific nature; d. in a natural mode. Hence someone can act against nature in four ways:

1. if, without concubitus, pollution is procured for the sake of venereal pleasure: solitary sin;

2. if concubitus is done toward the same sex, for example male with male or female with female: sodomy properly so called;

3. if concubitus is done with a thing of a different species: bestiality;

4. if the natural mode of lying together is not preserved, either by seeking an undue vessel or organ: sodomy improperly so called, or another undue mode in such a way, however, that generation is thereby impeded: onanism.

These differ in species according to a diverse repugnance toward nature and reason.¹

¹ Saint Thomas, II-II, q. 154, a. 11. Hence proposition 24 was condemned by Alexander VII: "Softness, sodomy, and bestiality are sins of the same lowest species; and therefore it suffices to say in confession that one has procured pollution."

II. Lust against nature, according to itself and other things being equal, is the gravest in the genus of lust, because it transgresses that which has been determined by nature itself concerning the use of the genitals as to their primary end. But the other sins of lust transgress only that which is further determined by reason. The first is more fundamental, because reason cannot determine certain things except according to those things which have first been determined by nature.

After this, however, is incest, which is also against a secondary natural inclination, namely against the natural reverence which we owe to persons joined to us. Adultery is graver than stuprum, because the injury is greater if someone abuses a person subject to the power of another for the use of generation than for guardianship alone; and simple fornication, which is committed without injury to another person, is least among the species of complete lust. By raptus and sacrilege, however, the aforesaid things can be aggravated.²

² Ibid., a. 12.

All these things are to be understood:

1. according to themselves, that is, according to their proper and distinct species; for per accidens several, indeed all, species of lust according to nature can concur in one act, so that in that act there is greater gravity than in one sin against nature;

2. formally, or in the genus of lust, without attending to the malice of another species. For in another genus, by reason of an added circumstance, other sins can become simply graver, for example adultery by reason of injustice is absolutely graver than pollution, and sacrilege by reason of irreligion; but pollution in the genus of lust is graver than both;

3. other things being equal, so that in equal circumstances a sin against nature is greater, and so that the greatest sin against nature is greater than the greatest according to nature.

Nevertheless nothing prevents some sin according to nature from being graver on the part of the agent, for instance because it is done from special malice or with greater audacity.

III. Among sins against nature, gravity is attended from the greater abuse rather than from the mere omission of due use. Hence bestiality is graver, because it recedes most of all from the rule of nature, since even the due species is not preserved; then sodomy properly so called, in which the due sex is not preserved; then sodomy improperly so called, or the undue mode of lying together, in which the due organ is not preserved; then onanism, or unnatural concubitus from the mode alone impeding generation. The lowest place is held by solitary sin, which is in the omission alone of concubitus toward another (ibid., a. 4).

Concerning these we must now speak in particular.