Whether the mixing with water is essential to this sacrament?
Objection 1: It seems that the mixing with water is essential to this sacrament. Because Cyprian says to Cecilius (Ep. lxiii): "Thus the Lord's chalice is not water only and wine only, but both must be mixed together: in the same way as neither the Lord's body be of flour only, except both," i.e. the flour and the water "be united as one." But the admixture of water with the flour is necessary for this sacrament. Consequently, for the like reason, so is the mixing of water with the wine.
Objection 2: Further, at our Lord's Passion, of which this is the memorial, water as well as blood flowed from His side. But wine, which is the sacrament of the blood, is necessary for this sacrament. For the same reason, therefore, so is water.
Objection 3: Further, if water were not essential to this sacrament, it would not matter in the least what kind of water was used; and so water distilled from roses, or any other kind might be employed; which is contrary to the usage of the Church. Consequently water is essential to this sacrament.
On the contrary, Cyprian says (Ep. lxiii): "If any of our predecessors, out of ignorance or simplicity, has not kept this usage," i.e. of mixing water with the wine, "one may pardon his simplicity"; which would not be the case if water were essential to the sacrament, as the wine or the bread. Therefore the mingling of water with the wine is not essential to the sacrament.
I answer that, Judgment concerning a sign is to be drawn from the thing signified. Now the adding of water to the wine is for the purpose of signifying the sharing of this sacrament by the faithful, in this respect that by the mixing of the water with the wine is signified the union of the people with Christ, as stated (A[6]). Moreover, the flowing of water from the side of Christ hanging on the cross refers to the same, because by the water is denoted the cleansing from sins, which was the effect of Christ's Passion. Now it was observed above (Q[73], A[1], ad 3), that this sacrament is completed in the consecration of the matter: while the usage of the faithful is not essential to the sacrament, but only a consequence thereof. Consequently, then, the adding of water is not essential to the sacrament.
Reply to Objection 1: Cyprian's expression is to be taken in the same sense in which we say that a thing cannot be, which cannot be suitably. And so the comparison refers to what ought to be done, not to what is essential to be done; since water is of the essence of bread, but not of the essence of wine.
Reply to Objection 2: The shedding of the blood belonged directly to Christ's Passion: for it is natural for blood to flow from a wounded human body. But the flowing of the water was not necessary for the Passion; but merely to show its effect, which is to wash away sins, and to refresh us from the heat of concupiscence. And therefore the water is not offered apart from the wine in this sacrament, as the wine is offered apart from the bread; but the water is offered mixed with the wine to show that the wine belongs of itself to this sacrament, as of its very essence; but the water as something added to the wine.
Reply to Objection 3: Since the mixing of water with the wine is not necessary for the sacrament, it does not matter, as to the essence of the sacrament, what kind of water is added to the wine, whether natural water, or artificial, as rose-water, although, as to the propriety of the sacrament, he would sin who mixes any other than natural and true water, because true water flowed from the side of Christ hanging on the cross, and not phlegm, as some have said, in order to show that Christ's body was truly composed of the four elements; as by the flowing blood, it was shown to be composed of the four humors, as Pope Innocent III says in a certain Decree. But because the mixing of water with flour is essential to this sacrament, as making the composition of bread, if rose-water, or any other liquor besides true water, be mixed with the flour, the sacrament would not be valid, because it would not be true bread.
Whether water should be added in great quantity?
Objection 1: It seems that water ought to be added in great quantity, because as blood flowed sensibly from Christ's side, so did water: hence it is written ( Jn. 19:35 ): "He that saw it, hath given testimony." But water could not be sensibly present in this sacrament except it were used in great quantity. Consequently it seems that water ought to be added in great quantity.
Objection 2: Further, a little water mixed with much wine is corrupted. But what is corrupted no longer exists. Therefore, it is the same thing to add a little water in this sacrament as to add none. But it is not lawful to add none. Therefore, neither is it lawful to add a little.
Objection 3: Further, if it sufficed to add a little, then as a consequence it would suffice to throw one drop of water into an entire cask. But this seems ridiculous. Therefore it does not suffice for a small quantity to be added.
On the contrary, It is said in the Decretals (Extra, De Celeb. Miss.): "The pernicious abuse has prevailed in your country of adding water in greater quantity than the wine, in the sacrifice, where according to the reasonable custom of the entire Church more wine than water ought to be employed."
I answer that, There is a threefold opinion regarding the water added to the wine, as Pope Innocent III says in a certain Decretal. For some say that the water remains by itself when the wine is changed into blood: but such an opinion cannot stand, because in the sacrament of the altar after the consecration there is nothing else save the body and the blood of Christ. Because, as Ambrose says in De Officiis (De Mysteriis ix): "Before the blessing it is another species that is named, after the blessing the Body is signified; otherwise it would not be adored with adoration of latria." And therefore others have said that as the wine is changed into blood, so the water is changed into the water which flowed from Christ's side. But this cannot be maintained reasonably, because according to this the water would be consecrated apart from the wine, as the wine is from the bread.
And therefore as he (Innocent III, Decretals, Extra, De Celeb. Miss.) says, the more probable opinion is that which holds that the water is changed into wine, and the wine into blood. Now, this could not be done unless so little water was used that it would be changed into wine. Consequently, it is always safer to add little water, especially if the wine be weak, because the sacrament could not be celebrated if there were such addition of water as to destroy the species of the wine. Hence Pope Julius I reprehends some who "keep throughout the year a linen cloth steeped in must, and at the time of sacrifice wash a part of it with water, and so make the offering."
Reply to Objection 1: For the signification of this sacrament it suffices for the water to be appreciable by sense when it is mixed with the wine: but it is not necessary for it to be sensible after the mingling.
Reply to Objection 2: If no water were added, the signification would be utterly excluded: but when the water is changed into wine, it is signified that the people is incorporated with Christ.
Reply to Objection 3: If water were added to a cask, it would not suffice for the signification of this sacrament, but the water must be added to the wine at the actual celebration of the sacrament.