Objection 1. It would seem that the species of sacrilege are not distinguished according to the sacred things. Material diversity does not differentiate species, if the formal aspect remains the same. Now there would seem to be the same formal aspect of sin in all violations of sacred things, and that the only difference is one of matter. Therefore the species of sacrilege are not distinguished thereby.
Objection 2. Further, it does not seem possible that things belonging to the same species should at the same time differ specifically. Now murder, theft, and unlawful intercourse, are different species of sin. Therefore they cannot belong to the one same species of sacrilege: and consequently it seems that the species of sacrilege are distinguished in accordance with the species of other sins, and not according to the various sacred things.
Objection 3. Further, among sacred things sacred persons are reckoned. If, therefore, one species of sacrilege arises from the violation of a sacred person, it would follow that every sin committed by a sacred person is a sacrilege, since every sin violates the person of the sinner. Therefore the species of sacrilege are not reckoned according to the sacred things.
On the contrary, Acts and habits are distinguished by their objects. Now the sacred thing is the object of sacrilege, as stated above (Article 1). Therefore the species of sacrilege are distinguished according to the sacred things.
I answer that, As stated above (Article 1), the sin of sacrilege consists in the irreverent treatment of a sacred thing. Now reverence is due to a sacred thing by reason of its holiness: and consequently the species of sacrilege must needs be distinguished according to the different aspects of sanctity in the sacred things which are treated irreverently: for the greater the holiness ascribed to the sacred thing that is sinned against, the more grievous the sacrilege.
Now holiness is ascribed, not only to sacred persons, namely, those who are consecrated to the divine worship, but also to sacred places and to certain other sacred things. And the holiness of a place is directed to the holiness of man, who worships God in a holy place. For it is written (2 Maccabees 5:19): "God did not choose the people for the place's sake, but the place for the people's sake." Hence sacrilege committed against a sacred person is a graver sin than that which is committed against a sacred place. Yet in either species there are various degrees of sacrilege, according to differences of sacred persons and places.
In like manner the third species of sacrilege, which is committed against other sacred things, has various degrees, according to the differences of sacred things. Among these the highest place belongs to the sacraments whereby man is sanctified: chief of which is the sacrament of the Eucharist, for it contains Christ Himself. Wherefore the sacrilege that is committed against this sacrament is the gravest of all. The second place, after the sacraments, belongs to the vessels consecrated for the administration of the sacraments; also sacred images, and the relics of the saints, wherein the very persons of the saints, so to speak, are reverenced and honored. After these come things connected with the apparel of the Church and its ministers; and those things, whether movable or immovable, that are deputed to the upkeep of the ministers. And whoever sins against any one of the aforesaid incurs the crime of sacrilege.
Reply to Objection 1. There is not the same aspect of holiness in all the aforesaid: wherefore the diversity of sacred things is not only a material, but also a formal difference.
Reply to Objection 2. Nothing hinders two things from belonging to one species in one respect, and to different species in another respect. Thus Socrates and Plato belong to the one species, "animal," but differ in the species "colored thing," if one be white and the other black. On like manner it is possible for two sins to differ specifically as to their material acts, and to belong to the same species as regards the one formal aspect of sacrilege: for instance, the violation of a nun by blows or by copulation.
Reply to Objection 3. Every sin committed by a sacred person is a sacrilege materially and accidentally as it were. Hence Jerome [The quotation is from St. Bernard, De Consideration, ii, 13 says that "a trifle on a priest's lips is a sacrilege or a blasphemy." But formally and properly speaking a sin committed by a sacred person is a sacrilege only when it is committed against his holiness, for instance if a virgin consecrated to God be guilty of fornication: and the same is to be said of other instances.
Source: Summa Theologica (New Advent)