Taken from THE CATECHISM EXPLAINED
Written by Fr. Francis Spirago; Edited by Fr. Richard Clarke, SJ
with Nihau Obstat and Imprimatur, New York, 1927
SECTION A: THE COMMANDMENTS
II. THE TWO COMMANDMENTS OF CHARITY
1. The most important commandments are the two commandmEnts of charity, that is to say, the love of God and the love of one's neighbor, for all the other commandments are comprised in them.
When Christ was once asked by of the Scribes which was the first of all the commandments, He answered: "Thou shalt love the Lord thy God with thy whole heart (i.e.. with the will) and with thy whole soul (i.e., with the understanding) and with thy whole mind (i.e., with the affections) and with thy whole strength (i.e., in all thy actions). This is the first commandment. And the second is like unto it: "Thou shalt love thy neighbor as thyself" (Mark xii. 30, 31). The same precepts were given to the Jews (Deut. vi. 5; Lev. xix. 18). These two commandments contain all the others, because they influence and direct all the powers of the soul of man; the understanding, the affections, the will, and all his actions besides. Thus he who fulfills these two commandments of charity keeps all the commandments; were they everywhere observed no other law would be necessary in the State or in the family. Hence Christ says: " On these two commandments dependeth the whole law and the prophets" (Matt. xxii. 40). The other commandments do but inculcate in detail what the commandments of charity enjoin.
In the command to love God the first four of the commandments of God are comprised; the other commandments of God and the obligation to perform works of mercy are comprehended in the second.
The first four commandments contain our duty to God. As our supreme Ruler He requires of us in the First Commandment worship and fidelity; in the Second, respect; in the Third, service; in the Fourth, respect towards His representatives upon earth. The other six enjoin on us our duty to our neighbor, forbidding us to injure him as regards his life in the Fifth; his purity in the Sixth; his property in the Seventh; his honor in the Eighth; his family in the Ninth and Tenth. The precept of Our Lord enjoining on us the performing of works of mercy (Matt. xxv. 31 seq.) is an amplification of the second commandment of charity, for it requires us to help our neighbor in his need. That the last six commandments of the Decalogue are a connected whole we gather from Our Lord's answer to the rich young man (Matt. xix. 18). St. Paul also classes them together (Rom. xiii. 9).
2. Without the love of God and of our neighbor no man can be saved.
St. John says: "He that loveth not, abideth in death" (1 John iii. 14). St. Augustine says that as we require two feet to walk, so we must have the love of God and of our neighbor if we would reach Heaven, and enter into the presence of God. As the bird cannot fly without two wings, so must we be borne aloft upon these two pinions if we would soar up to Heaven. The blessed in Heaven love God and one another; we must do the same here on earth if we are to join their blissful company. "What is man, O God," asks St. Augustine, "that Thou dost command him to love Thee, and threaten him with terrible chastisements if he fails to do so?"
3. The capacity for loving God and our neighbor is bestowed upon us simultaneously with sanctifying grace.
Of ourselves we are incapable of loving God above all things.
Ever since the blight of Original Sin fell upon us, it is with our heart as with the date-palm, which transplanted to a colder clime does indeed bear fruit, but cannot produce the ripe and delicious dates of the land where it is indigenous. So our hearts would fain love God, but the power is lacking to them; they can only attain to true charity when informed by Divine grace. "To will is present with me, but how to accomplish that which is good I know not" (Rom. vii. 18)., Not until the Holy Spirit takes possession of us by Baptism or penance is the love of God shed abroad in our heart. The love of our neighbor is implanted within us at the same time as the love of God; they are but one, the only difference is in the object towards which they are directed. The love of God and of our neighbor may be compared to two streams, issuing from one and the self-same source. St. Augustine says that Christ gave the Holy Spirit to the Apostles twice (when He breathed upon them and on the Day of Pentecost) because with the Holy Spirit a twofold charity is imparted to us
4. The love of God is inseparably united to the love of our neighbor.
As the plant is contained within the seed, so the love of our neighbor is comprised in the love of God. The two precepts are so constituted that the one cannot be observed without the other. This is 'why Holy Scripture speaks of one commandment of charity. "If any man says I love God, and hateth his brother, he is a liar" (1 John xiv. 20). Our love of our neighbor is therefore the best test of our love of God. He who cherishes ill-will towards his fellow-man, who hates him, envies him, injures him in any way, or who grudges alms to the needy, is destitute of the love of God. The greater our love of God, the greater will be our love of our neighbor.