Theory and practice of the confessional by Caspar Erich Schieler, Richard Frederick Clarke
2. Humilis. Let the confession be humble, for a man approaches the tribunal as a penitent, as one guilty of crime, as one accusing himself to his judge and seeking grace and mercy; of such a one humility and lowliness are to be expected. Surely the knowledge of one's sins and sinfulness revealed by an honest examination of the conscience, the remembrance of repeated unfaithfulness and ingratitude to God, are reason enough for being humble. Let this humility fill the heart, pervade the accusation, be manifested in the whole exterior; then let the penitent go into the confessional, kneeling, with head uncovered, like the publican in the Gospel, who remained by the door of the Temple and dared not to raise his eyes to heaven, but struck his breast and prayed: " God, be merciful to me a sinner." The words used by some are very appropriate as an introduction to the confession: "I, a poor sinner, confess and acknowledge to God, and to you, reverend father, in God's place, that I have sinned often and grievously by thought, word, deed, and omission'' etc. Others, again, use the words of the Confiteor: " I confess to almighty God, to Blessed Mary, ever a virgin, . . . that I have sinned exceedingly in thought, word, and deed," etc.
3. Pura. The confession should be made with the object of gaining pardon of sin and the grace of the Sacrament. If it were made with any wicked and gravely sinful intention, it would be a sacrilegious and invalid confession; if the penitent had any venially sinful object in view, e.g. to gain esteem, the confession would be valid though the penitent would incur the guilt of venial sin by it. If the penitent's principal intention is to be reconciled to God, though at the same time there be present other motives not altogether forbidden, the confession is unimpaired ; the same may easily happen in other good works, and secondary motives do not exclude the principal one.
4. Fidelis (seu verax). The confession should be truthful and candid, without lies and deceit. Hence the penitent must not conceal the sins he has committed, nor confess those which he has not committed; neither may he confess as certain what is doubtful, nor what is doubtful as certain. It is disputed whether every lie in confession is a mortal sin and renders the confession null. There are indeed theologians who maintain that every lie told in confession is a mortal sin, because of the sin being committed in the very act of receiving a Sacrament. This view, however, is wrong. It is true that any lie told in confession is more sinful than the same lie told under other circumstances would be, on account of the irreverence to the Sacrament; but mortal sin would be incurred only by a lie in confession when the lie concerns the materia necessaria of confession; in such a case the confession is invalid, for the judge is deceived about the case, and that is gravely wrong. If the penitent lies to the confessor in a matter which does not pertain to the Sacrament, there is no mortal sin, for such a lie does not mislead the judge nor imply a grave irreverence to the Sacrament, since still there is real matter for the Sacrament and a sufficient disposition to obtain the grace of the Sacrament. Accordingly, if the lie told in confession has nothing to do with the confession itself, it is mortal or venial on its own merits quite apart from the circumstances of its being told in confession.