(a) the contrition required for the matter and the validity of the Sacrament must be such as can be known with moral certainty by the confessor from external indications, and hence it suffices for validity that the sorrow be true and sincere and supernatural;
(b) the contrition required for the disposition of the penitent and the fruitfulness of the Sacrament must be such as excludes all affection for every grave sin and includes the resolution to avoid all mortal sin in the future, and hence it is required for fruitfulness that sorrow be also universal and sovereign. (This opinion has very few, if any at all, adherents among modern theologians. It is retained here solely as a matter of record.)
2735. Properties of Contrition.—Since contrition belongs to the matter of Penance, it must have the properties of sacramental matter (2655 sqq.).
(a) Thus, the matter must be sensible, and hence contrition must be shown in some external way, as by a sorrowful confession, devout request for absolution, or, in the case of those who are unconscious, by a call for a priest or the practices or prayers of a Christian life.
(b) The matter must be united with the form, and hence contrition must be elicited at the moment of absolution, or a short time before (not more than a few hours before, according to some, or even a few days before, according to others). But if a penitent recalls immediately after absolution a forgotten mortal sin, and is then absolved from it also, more probably he is not obliged to renew his act of contrition, because the act just made virtually continues; in practice, however, he might be told to make another act of contrition and a new penance or the same penance may be imposed before the second absolution. Moreover, for absolution when one is unconscious and in danger of death, since an habitual intention suffices (2674), it seems that contrition made long ago, but not retracted, is sufficient.
(c) The matter must have at least a moral unity of its own parts, and hence the contrition must in some way be directed to the confession; that is, either before or during or after the act of contrition there must be an intention to confess with the sorrow for sin contained in that act of contrition, or to apply that sorrow to the confession just made. Otherwise it does not appear that one has the purpose to make a sacramental confession. But there is no practical difficulty, as every act of contrition contains implicitly the will to confess, or every sincere confession includes the will to use the contrition one has exercised or will exercise.
2736. Resolution of Amendment.—The resolution of amendment which true contrition calls for is at least implicit in the hatred of sin, but it is advisable that the penitent expressly resolve to avoid sin in the future. This determination should have the following qualities:
(a) it should be firm, that is, the penitent should make up his mind not to relapse into deliberate sin. Yet, it is not necessary that he feel certain of his perseverance, and his resolve does not cease to be firm, if he foresees that he will fall again, provided he is decided to do the best he can;
(b) it should be efficacious, that is, the penitent must decide to use suitable means to fulfill his good intentions as to reparation for scandal, calumny, and injustice, as to the avoidance of sinful occasions, etc.;
(c) it should be universal, that is, the penitent must resolve at least generically to avoid each and every grave sin in the future. If only free matter (2727) is confessed, the penitent may direct his resolution of amendment to all past mortal sins confessed, or to one of the present venial sins declared, or he may resolve to do better in reference to a certain class of sins (e.g., deliberate sins, faults of speech), or he may resolve to diminish the frequency of his venial sins.