Objection 1. It would seem that the conditions assigned by masters, and contained in the following lines, are not requisite for confession:
Simple, humble, pure, faithful,
Frequent, undisguised, discreet, voluntary, shamefaced,
Entire, secret, tearful, not delayed,
Courageously accusing, ready to obey.
courage
virtues
conditions
Objection 2. Further, a thing is "pure" when it is not mixed with anything else: and "simplicity," in like manner, removes composition and admixture. Therefore one or the other is superfluous.
Objection 3. Further, no one is bound to confess more than once a sin which he has committed but once. Therefore if a man does not commit a sin again, his penance need not be "frequent."
Objection 4. Further, confession is directed to satisfaction. But satisfaction is sometimes public. Therefore confession should not always be "secret."
Objection 5. Further, that which is not in our power is not required of us. But it is not in our power to shed "tears." Therefore it is not required of those who confess.
On the contrary, We have the authority of the masters who assigned the above.
I answer that, Some of the above conditions are essential to confession, and some are requisite for its well-being. Now those things which are essential to confession belong to it either as to an act of virtue, or as to part of a sacrament. If in the first way, it is either by reason of virtue in general, or by reason of the special virtue of which it is the act, or by reason of the act itself. Now there are four conditions of virtue in general, as stated in Ethic. ii, 4. The first is knowledge, in respect of which confession is said to be "discreet," inasmuch as prudence is required in every act of virtue: and this discretion consists in giving greater weight to greater sins. The second condition is choice, because acts of virtue should be voluntary, and in this respect confession is said to be "voluntary." The third condition is that the act be done for a particular purpose, viz. the due end, and in this respect confession is said to be "pure," i.e. with a right intention. The fourth condition is that one should act immovably, and in this respect it is said that confession should be "courageous," viz. that the truth should not be forsaken through shame.
Now confession is an act of the virtue of penance. First of all it takes its origin in the horror which one conceives for the shamefulness of sin, and in this respect confession should be "full of shame," so as not to be a boastful account of one's sins, by reason of some worldly vanity accompanying it. Then it goes on to deplore the sin committed, and in this respect it is said to be "tearful." Thirdly, it culminates in self-abjection, and in this respect it should be "humble," so that one confesses one's misery and weakness.
By reason of its very nature, viz. confession, this act is one of manifestation: which manifestation can be hindered by four things: first, by falsehood, and in this respect confession is said to be "faithful," i.e. true. Secondly, by the use of vague words, and against this confession is said to be "open," so as not to be wrapped up in vague words; thirdly, by "multiplicity" of words, in which respect it is said to be "simple" indicating that the penitent should relate only such matters as affect the gravity of the sin; fourthly none of those things should be suppressed which should be made known, and in this respect confession should be "entire."
In so far as confession is part of a sacrament it is subject to the judgment of the priest who is the minister of the sacrament. Wherefore it should be an "accusation" on the part of the penitent, should manifest his "readiness to obey" the priest, should be "secret" as regards the nature of the court wherein the hidden affairs of conscience are tried.
The well-being of confession requires that it should be "frequent"; and "not delayed," i.e. that the sinner should confess at once.
Reply to Objection 1. There is nothing unreasonable in one virtue being a condition of the act of another virtue, through this act being commanded by that virtue; or through the mean which belongs to one virtue principally, belonging to other virtues by participation.
Reply to Objection 2. The condition "pure" excludes perversity of intention, from which man is cleansed: but the condition "simple" excludes the introduction of unnecessary matter.
Reply to Objection 3. This is not necessary for confession, but is a condition of its well-being.
Reply to Objection 4. Confession should be made not publicly but privately, lest others be scandalized, and led to do evil through hearing the sins confessed. On the other hand, the penance enjoined in satisfaction does not give rise to scandal, since like works of satisfaction are done sometimes for slight sins, and sometimes for none at all.
Reply to Objection 5. We must understand this to refer to tears of the heart.
Source: Summa Theologica (New Advent)