Rogier Van der Weyden, Seven Sacraments (ca 1445-50)
Quaeritur: Which is the most important of Sacraments? The Council of Trent, in Canon 3 of Session 7, says we should not consider all the Sacraments to be equally excellent. So naturally there arises the question of which of the Sacraments is the most important.
I have had many encounters with people who have disagreed on what is the most excellent Sacrament. They usually tend to get into some impossible argument from causality. It usually goes something like this:
Person 1: What is the most important Sacrament?
Person 2: It must be the Eucharist, because it's Christ himself!
Person 1: But without an ordained priest you would have no Eucharist, so isn't Holy Orders more important?
Person 2: OK, but without the family no future priests would be born, so doesn't marriage have precedence?
What is the best way of settling this question?
Respondeo: Indeed, Trent taught that: "If any one saith, that these seven Sacraments are in such wise equal to each other, as that one is not in any way more worthy than another; let him be anathema" (Session 7, Can. 3). At least everyone in the conversation agrees that not all Sacraments are of the same worthiness or excellence. But which one is higher or more important than the others, and what is their order, is a bit more complex.
St. Thomas has a very nuanced way of resolving this issue. First, we need to make a distinction: "importance" (or "excellence" or "nobility," etc.) and "precedence in causality" are not the same. Christ could not have been born without Adam, but that doesn't make Adam more 'important' than Christ.
So in terms of excellence or importance, you are right in saying that the Holy Eucharist is Christ himself, the Author of grace, whereas the rest of the Sacraments are instrumental causes of grace, and thus, absolutely speaking (simpliciter), the Holy Eucharist is the greatest, noblest, and most excellent Sacrament. This is so primarily for the reason that the other Sacraments are creatures, and all creatures are inferior to their Creator. Moreover, all Sacraments are ordered to the Holy Eucharist as to their end, and even ritually terminate with the Eucharist (i.e., a Mass is normally offered after each of the Sacraments).
Yet, when considered in one respect or another (secundum quid), some Sacraments may have precedence as compared to others. For example, Baptism is the greatest in terms of necessity for salvation. Holy Order is the greatest in terms of the character it confers upon the recipient.
Even Marriage is greatest in one respect, namely, its signification: "As regards what is signified [...] marriage is the noblest, because it signifies the conjunction of the two natures in the person of Christ” (In IV Sent., d. 7, q. 1, a. 1, qa. 3; Cf. Peter Kwasniewski, "St. Thomas on the Grandeur and Limitations of Marriage," Nova et Vetera 10 (2012), 415-36).
But yes, simpliciter they are all ultimately inferior to the Holy Eucharist, the Body and Blood of the Son of God Himself.
St. Thomas summarizes this teaching beautifully in Summa theologiae, IIIa, q. 65, a. 3, c & ad 4:
|Respondeo dicendum quod, simpliciter loquendo, sacramentum Eucharistiae est potissimum inter alia sacramenta. Quod quidem tripliciter apparet. Primo quidem, ex eo quod in eo continetur ipse Christus substantialiter, in aliis autem sacramentis continetur quaedam virtus instrumentalis participata a Christo, ut ex supra dictis patet. Semper autem quod est per essentiam, potius est eo quod est per participationem.||I answer that, Absolutely speaking, the sacrament of the Eucharist is the greatest of all the sacraments: and this may be shown in three ways. First of all because it contains Christ Himself substantially: whereas the other sacraments contain a certain instrumental power which is a share of Christ's power, as we have shown above (Question , Article , ad 3, Article ). Now that which is essentially such is always of more account than that which is such by participation.|
|Secundo hoc apparet ex ordine sacramentorum ad invicem, nam omnia alia sacramenta ordinari videntur ad hoc sacramentum sicut ad finem. Manifestum est enim quod sacramentum ordinis ordinatur ad Eucharistiae consecrationem. Sacramentum vero Baptismi ordinatur ad Eucharistiae receptionem. In quo etiam perficitur aliquis per confirmationem, ut non vereatur se subtrahere a tali sacramento. Per poenitentiam etiam et extremam unctionem praeparatur homo ad digne sumendum corpus Christi. Matrimonium autem saltem sua significatione attingit hoc sacramentum, inquantum significat coniunctionem Christi et Ecclesiae, cuius unitas per sacramentum Eucharistiae figuratur, unde et apostolus dicit, Ephes. V, sacramentum hoc magnum est, ego autem dico in Christo et in Ecclesia.||Secondly, this is made clear by considering the relation of the sacraments to one another. For all the other sacraments seem to be ordained to this one as to their end. For it is manifest that the sacrament of order is ordained to the consecration of the Eucharist: and the sacrament of Baptism to the reception of the Eucharist: while a man is perfected by Confirmation, so as not to fear to abstain from this sacrament. By Penance and Extreme Unction man is prepared to receive the Body of Christ worthily. And Matrimony at least in its signification, touches this sacrament; in so far as it signifies the union of Christ with the Church, of which union the Eucharist is a figure: hence the Apostle says (Eph. 5:32): "This is a great sacrament: but I speak in Christ and in the Church."|
|Tertio hoc apparet ex ritu sacramentorum. Nam fere omnia sacramenta in Eucharistia consummantur, ut dicit Dionysius, III cap. Eccles. Hier., sicut patet quod ordinati communicant, et etiam baptizati si sint adulti.||Thirdly, this is made clear by considering the rites of the sacraments. For nearly all the sacraments terminate in the Eucharist, as Dionysius says (Eccl. Hier. iii): thus those who have been ordained receive Holy Communion, as also do those who have been baptized, if they be adults.|
|Aliorum autem sacramentorum comparatio ad invicem potest esse multipliciter. Nam in via necessitatis, Baptismus est potissimum sacramentorum; in via autem perfectionis, sacramentum ordinis; medio autem modo se habet sacramentum confirmationis. Sacramentum vero poenitentiae et extremae unctionis sunt inferioris gradus a praedictis sacramentis, quia, sicut dictum est, ordinantur ad vitam Christianam non per se, sed quasi per accidens, scilicet in remedium supervenientis defectus. Inter quae tamen extrema unctio comparatur ad poenitentiam sicut confirmatio ad Baptismum, ita scilicet quod poenitentia est maioris necessitatis, sed extrema unctio est maioris perfectionis.||The remaining sacraments may be compared to one another in several ways. For on the ground of necessity, Baptism is the greatest of the sacraments; while from the point of view of perfection, order comes first; while Confirmation holds a middle place. The sacraments of Penance and Extreme Unction are on a degree inferior to those mentioned above; because, as stated above (Article ), they are ordained to the Christian life, not directly, but accidentally, as it were, that is to say, as remedies against supervening defects. And among these, Extreme Unction is compared to Penance, as Confirmation to Baptism; in such a way, that Penance is more necessary, whereas Extreme Unction is more perfect.|
|Ad quartum dicendum quod [...] Baptismus, cum sit maximae necessitatis, est potissimum sacramentorum. Sicut ordo et confirmatio habent quandam excellentiam ratione ministerii; et matrimonium ratione significationis. Nihil enim prohibet aliquid esse secundum quid dignius, quod tamen non est dignius simpliciter.||Reply to Objection 4: [...] Baptism, being of the greatest necessity, is the greatest of the sacraments, just as order and Confirmation have a certain excellence considered in their administration; and Matrimony by reason of its signification. For there is no reason why a thing should not be greater from a certain point of view which is not greater absolutely speaking.|