Objection 1: It would seem that backbiting is a graver sin than tale-bearing. For sins of word consist in speaking evil. Now a backbiter speaks of his neighbor things that are evil simply, for such things lead to the loss or depreciation of his good name: whereas a tale-bearer is only intent on saying what is apparently evil, because to wit they are unpleasant to the hearer. Therefore backbiting is a graver sin than tale-bearing.
Obj. 2: Further, he that deprives a man of his good name, deprives him not merely of one friend, but of many, because everyone is minded to scorn the friendship of a person with a bad name. Hence it is reproached against a certain individual [*King Josaphat] (2 Paralip. 19:2): "Thou art joined in friendship with them that hate the Lord." But tale-bearing deprives one of only one friend. Therefore backbiting is a graver sin than tale-bearing.
Obj. 3: Further, it is written (James 4:11): "He that backbiteth [Douay: 'detracteth'] his brother . . . detracteth the law," and consequently God the giver of the law. Wherefore the sin of backbiting seems to be a sin against God, which is most grievous, as stated above (Q. 20, A. 3; I-II, Q. 73, A. 3). On the other hand the sin of tale-bearing is against one's neighbor. Therefore the sin of backbiting is graver than the sin of tale-bearing.
On the contrary, It is written (Ecclus. 5:17): "An evil mark of disgrace is upon the double-tongued; but to the tale-bearer [Douay: 'whisperer'] hatred, and enmity, and reproach."
I answer that, As stated above (Q. 73, A. 3; I-II, Q. 73, A. 8), sins against one's neighbor are the more grievous, according as they inflict a greater injury on him: and an injury is so much the greater, according to the greatness of the good which it takes away. Now of all one's external goods a friend takes the first place, since "no man can live without friends," as the Philosopher declares (Ethic. viii, 1). Hence it is written (Ecclus. 6:15): "Nothing can be compared to a faithful friend." Again, a man's good name whereof backbiting deprives him, is most necessary to him that he may be fitted for friendship. Therefore tale-bearing is a greater sin than backbiting or even reviling, because a friend is better than honor, and to be loved is better than to be honored, according to the Philosopher (Ethic. viii).
Reply Obj. 1: The species and gravity of a sin depend on the end rather than on the material object, wherefore, by reason of its end, tale-bearing is worse than backbiting, although sometimes the backbiter says worse things.
Reply Obj. 2: A good name is a disposition for friendship, and a bad name is a disposition for enmity. But a disposition falls short of the thing for which it disposes. Hence to do anything that leads to a disposition for enmity is a less grievous sin than to do what conduces directly to enmity.
Reply Obj. 3: He that backbites his brother, seems to detract the law, in so far as he despises the precept of love for one's neighbor: while he that strives to sever friendship seems to act more directly against this precept. Hence the latter sin is more specially against God, because "God is charity" (1 John 4:16), and for this reason it is written (Prov. 6:16): "Six things there are, which the Lord hateth, and the seventh His soul detesteth," and the seventh is "he (Prov. 6:19) that soweth discord among brethren."