Thomas Aquinas

Having set forth their exhortation for preserving ecclesiastical unity, in this part the Apostle suggests to the Ephesians themselves the form of the aforesaid unity. Here it must be known that, since the Church of God is like a city, it is something one and distinct, since it is not one as something simple, but as something composed of diverse parts. And therefore the Apostle does two things. First he shows what is common to the Church; second he shows what is distinct within it, at the place "but to each of us grace was given," etc. Now in any city, in order for it to be one, four things must be common: namely, one ruler, one law, the same insignia, and the same end. And the Apostle says these four things are in the Church.

He says therefore: I say that you ought to have one body and one spirit, because you are in the unity of the Church, which is one. First, because it has one leader, namely Christ, and as to this he says "one Lord" — not many, for whose diverse wills you would have to be in discord. For it is said in Hebrews 3:6: "Christ is as a son in his own house." Acts 2:36: "Let all the house of Israel therefore know most certainly, that God has made him both Lord and Christ, this Jesus whom you crucified." 1 Corinthians 8:6: "one Lord of ours, Jesus Christ." Zechariah 14:9: "In that day there shall be one Lord, and his name one."

Second, because his law is one. For the law of the Church is the law of faith. Romans 3:27: "Where then is your boasting now? It is excluded. Through what law? Of works? No, but through the law of faith." But "faith" is sometimes taken for the very thing believed, according to that: "this is the Catholic faith," etc., that is, these things ought to be believed. But sometimes it is taken for the habit of faith, by which one believes in the heart. And this can be said of both. Concerning the first, so that the sense is "faith is one," that is, you are commanded to believe the same thing and to work in the same way, because it is one and the same thing that is believed by all the faithful, whence it is called universal or Catholic. Hence 1 Corinthians 1:10: "that you all say the same thing," that is, think, etc. In another way, "faith is one," that is, one habit of faith by which one believes; one, I say, not numerically, but in species, because it ought to be the same in the hearts of all; and in this way the same will of those willing is called one will.

Third, the insignia of the Church are the same, namely the sacraments of Christ, among which the first is Baptism, which is the door of all the others. And therefore he says "one Baptism." Now it is said to be one for a threefold reason. First, because baptisms do not differ according to those who baptize; for by whomever they are conferred, they have a uniform power, because he who baptizes inwardly is one, namely Christ. John 1:33: "Upon whomever you shall see the Spirit descending and remaining upon him, this is he who baptizes in the Holy Spirit." Second, it is said to be one because it is given in the name of one, namely the Trinity: "Baptizing them in the name of the Father, and of the Son, and of the Holy Spirit." Third, because it cannot be repeated. Now Penance, Matrimony, the Eucharist, and Extreme Unction can be repeated, but not Baptism. Hebrews 6:4: "It is impossible for those who were once enlightened," namely through Baptism, "and have tasted the heavenly gift, and were made partakers of the Holy Spirit, and have tasted nonetheless the good word of God and the powers of the world to come, and have fallen away," namely through sin, "to be renewed again to penance." But it is not repeated either because of the character, or because its cause is not repeated. Romans 6:4: "For we were buried together with him through Baptism into death," etc. But now Christ died once for sins, as is said in 1 Peter 3:18.

Fourth, in the Church there is the same end, which is God. For the Son leads us to the Father. 1 Corinthians 15:24: "When he shall have delivered up the kingdom to God and the Father, when he shall have brought to nothing all principality, and power, and virtue; but he must reign," etc. And as to this he adds, saying "one God," etc., where first the Apostle sets down his unity; second, his dignity, at the place "who is above all," etc.

Concerning the first he says two things: the first pertains to the divine nature; hence he says "one God." Deuteronomy 6:4: "Hear, O Israel, the Lord your God is one." The other pertains to his benevolence toward us and to piety; hence he says "and Father of all." Isaiah 63:16: "You, Lord, are our Father and our Redeemer." Malachi 2:10: "Is there not one Father of us all? Has not God created us?"

Now he commends his dignity from three things. From the height of his divinity, when he says "who is above all." Psalm 112:4: "The Lord is above all nations," etc. From the breadth of his power, when he says "through all." Jeremiah 33:24: "I fill heaven and earth," etc. Psalm 8:8: "You subjected all things under his feet," etc. Luke 10:22: "All things indeed have been delivered to me," inasmuch as "all things were made through him," John 1:3. But in the manner in which it is said in Wisdom 11:21: "You have disposed all things in number, and weight, and measure." From the largesse of grace, when he says "and in us all," namely through grace. Jeremiah 14:9: "But you are in us, O Lord," etc.

But the first is appropriated to the Father, who is the fontal principle of the divinity and excels all creatures. The second to the Son, who is the wisdom "reaching mightily from end to end," Wisdom 8:1. The third indeed to the Holy Spirit, who "fills the world," Wisdom 1:7.