Objection 1: It seems that the defects occurring during the celebration of this sacrament cannot be sufficiently met by observing the statutes of the Church. For it sometimes happens that before or after the consecration the priest dies or goes mad, or is hindered by some other infirmity from receiving the sacrament and completing the mass. Consequently it seems impossible to observe the Church's statute, whereby the priest consecrating must communicate of his own sacrifice.
Obj. 2: Further, it sometimes happens that, before the consecration, the priest remembers that he has eaten or drunk something, or that he is in mortal sin, or under excommunication, which he did not remember previously. Therefore, in such a dilemma a man must necessarily commit mortal sin by acting against the Church's statute, whether he receives or not.
Obj. 3: Further, it sometimes happens that a fly or a spider, or some other poisonous creature falls into the chalice after the consecration. Or even that the priest comes to know that poison has been put in by some evilly disposed person in order to kill him. Now in this instance, if he takes it, he appears to sin by killing himself, or by tempting God: also in like manner if he does not take it, he sins by acting against the Church's statute. Consequently, he seems to be perplexed, and under necessity of sinning, which is not becoming.
Obj. 4: Further, it sometimes happens from the server's want of heed that water is not added to the chalice, or even the wine overlooked, and that the priest discovers this. Therefore he seems to be perplexed likewise in this case, whether he receives the body without the blood, thus making the sacrifice to be incomplete, or whether he receives neither the body nor the blood.
Obj. 5: Further, it sometimes happens that the priest cannot remember having said the words of consecration, or other words which are uttered in the celebration of this sacrament. In this case he seems to sin, whether he repeats the words over the same matter, which words possibly he has said before, or whether he uses bread and wine which are not consecrated, as if they were consecrated.
Obj. 6: Further, it sometimes comes to pass owing to the cold that the host will slip from the priest's hands into the chalice, either before or after the breaking. In this case then the priest will not be able to comply with the Church's rite, either as to the breaking, or else as to this, that only a third part is put into the chalice.
Obj. 7: Further, sometimes, too, it happens, owing to the priest's want of care, that Christ's blood is spilled, or that he vomits the sacrament received, or that the consecrated hosts are kept so long that they become corrupt, or that they are nibbled by mice, or lost in any manner whatsoever; in which cases it does not seem possible for due reverence to be shown towards this sacrament, as the Church's ordinances require. It does not seem then that such defects or dangers can be met by keeping to the Church's statutes.
On the contrary, Just as God does not command an impossibility, so neither does the Church.
I answer that, Dangers or defects happening to this sacrament can be met in two ways: first, by preventing any such mishaps from occurring: secondly, by dealing with them in such a way, that what may have happened amiss is put right, either by employing a remedy, or at least by repentance on his part who has acted negligently regarding this sacrament.
Reply Obj. 1: If the priest be stricken by death or grave sickness before the consecration of our Lord's body and blood, there is no need for it to be completed by another. But if this happens after the consecration is begun, for instance, when the body has been consecrated and before the consecration of the blood, or even after both have been consecrated, then the celebration of the mass ought to be finished by someone else. Hence, as is laid down (Decretal vii, q. 1), we read the following decree of the (Seventh) Council of Toledo: "We consider it to be fitting that when the sacred mysteries are consecrated by priests during the time of mass, if any sickness supervenes, in consequence of which they cannot finish the mystery begun, let it be free for the bishop or another priest to finish the consecration of the office thus begun. For nothing else is suitable for completing the mysteries commenced, unless the consecration be completed either by the priest who began it, or by the one who follows him: because they cannot be completed except they be performed in perfect order. For since we are all one in Christ, the change of persons makes no difference, since unity of faith insures the happy issue of the mystery. Yet let not the course we propose for cases of natural debility, be presumptuously abused: and let no minister or priest presume ever to leave the Divine offices unfinished, unless he be absolutely prevented from continuing. If anyone shall have rashly presumed to do so, he will incur sentence of excommunication."