I answer that, Virginity takes its name apparently from viror (freshness), and just as a thing is described as fresh and retaining its freshness, so long as it is not parched by excessive heat, so too, virginity denotes that the person possessed thereof is unseared by the heat of concupiscence which is experienced in achieving the greatest bodily pleasure which is that of sexual intercourse. Hence, Ambrose says (De Virgin. i, 5) that "virginal chastity is integrity free of pollution."
Now venereal pleasures offer three points for consideration. The first is on the part of the body, viz. the violation of the seal of virginity. The second is the link between that which concerns the soul and that which concerns the body, and this is the resolution of the semen, causing sensible pleasure. The third is entirely on the part of the soul, namely the purpose of attaining this pleasure. Of these three the first is accidental to the moral act, which as such must be considered in reference to the soul. The second stands in the relation of matter to the moral act, since the sensible passions are the matters of moral acts. But the third stands in the position of form and complement, because the essence of morality is perfected in that which concerns the reason. Since then virginity consists in freedom from the aforesaid corruption, it follows that the integrity of the bodily organ is accidental to virginity; while freedom from pleasure in resolution of the semen is related thereto materially; and the purpose of perpetually abstaining from this pleasure is the formal and completive element in virginity.
Reply Obj. 1: This definition of Augustine's expresses directly that which is formal in virginity. For "meditation" denotes reason's purpose; and the addition "perpetual" does not imply that a virgin must always retain this meditation actually, but that she should bear in mind the purpose of always persevering therein. The material element is expressed indirectly by the words "on incorruption in a corruptible body." This is added to show the difficulty of virginity: for if the flesh were incorruptible, it would not be difficult to maintain a perpetual meditation on incorruption.
Reply Obj. 2: It is true that purity, as to its essence, is in the soul; but as to its matter, it is in the body: and it is the same with virginity. Wherefore Augustine says (De Virgin. viii) that "although virginity resides in the flesh," and for this reason is a bodily quality, "yet it is a spiritual thing, which a holy continency fosters and preserves."
Reply Obj. 3: As stated above, the integrity of a bodily organ is accidental to virginity, in so far as a person, through purposely abstaining from venereal pleasure, retains the integrity of a bodily organ. Hence if the organ lose its integrity by chance in some other way, this is no more prejudicial to virginity than being deprived of a hand or foot.
Reply Obj. 4: Pleasure resulting from resolution of semen may arise in two ways. If this be the result of the mind's purpose, it destroys virginity, whether copulation takes place or not. Augustine, however, mentions copulation, because such like resolution is the ordinary and natural result thereof. In another way this may happen beside the purpose of the mind, either during sleep, or through violence and without the mind's consent, although the flesh derives pleasure from it, or again through weakness of nature, as in the case of those who are subject to a flow of semen. In such cases virginity is not forfeit, because such like pollution is not the result of impurity which excludes virginity. _______________________
SECOND ARTICLE [II-II, Q. 152, Art. 2]
Whether Virginity Is Unlawful?
Objection 1: It would seem that virginity is unlawful. For whatever is contrary to a precept of the natural law is unlawful. Now just as the words of Gen. 2:16, "Of every tree" that is in "paradise, thou shalt eat," indicate a precept of the natural law, in reference to the preservation of the individual, so also the words of Gen. 1:28, "Increase and multiply, and fill the earth," express a precept of the natural law, in reference to the preservation of the species. Therefore just as it would be a sin to abstain from all food, as this would be to act counter to the good of the individual, so too it is a sin to abstain altogether from the act of procreation, for this is to act against the good of the species.
Obj. 2: Further, whatever declines from the mean of virtue is apparently sinful. Now virginity declines from the mean of virtue, since it abstains from all venereal pleasures: for the Philosopher says (Ethic. ii, 2), that "he who revels in every pleasure, and abstains from not even one, is intemperate: but he who refrains from all is loutish and insensible." Therefore virginity is something sinful.