To make the growth of Catholicism intelligible to his hearers, Jesus compares the kingdom of heaven with a grain of mustard, which unfolds the least of all seeds to a stately tree. Immediately thereafter it is said that the kingdom of heaven penetrates the mass of humanity like leaven. The law of development of Catholicism is further illustrated by the following parable: The earth, says Jesus, bringeth forth fruit; first the blade, then the ear, afterward the full corn in the ear; man has but to cast the seed into the earth; then he may sleep, and the seed shall [{672}] spring and grow up, he knoweth not how. Even so is the kingdom of God. The Church therefore carries the germs of her growth in her inmost nature. Catholicism is gradually developed out of itself, from within. Thanks to the energy of her own principle, the Church with her arms encircles nation after nation. The faculty of being all things unto all men she owes to her being the kingdom of God. Here is the root of Catholicism. As the kingdom of God, the Church is fraught with a wealth adequate to the mental requirements of all individuals and all nations. As the kingdom of God, the Church is adapted to every age and clime.
The word "Church" is used by Jesus Christ far more rarely than that of the "kingdom of heaven;" indeed but twice, and on each occasion in direct reference to the external form of the Church.
That this historical exterior of Catholicism, designated the Church, is the manifestation of the kingdom of God, We have already deduced from Matt. xvi. 18, 19, and xiii. 41. The same truth is expressed in the parable of the treasure hid in the field. He who would possess the treasure, that is to say, the kingdom of heaven, or the vital principle of Catholicism, must buy the field in which the gem is concealed. The field, the Catholic exterior of the Church, is not the inner life; but the latter is realized only in the historical form of Catholicism.
It now behooves us to more precisely expound this relation between the spirit and the outer form of the Church from the words of Jesus. The way to do this is indicated by our Lord himself. It consists in an extended analysis of the biblical idea of the kingdom of God. In it is disclosed the inmost nature of the Church and thereby the ultimate origin of her historical figure as instituted by Christ, or the principle of Catholicism, which is the object of our search.
My kingdom, says the Lord, is not of this world; that is to say, its origin is not here, and it is not established by the exercise of worldly power. Regnum meum non est hinc. True, the kingdom of Christ is established in the midst of the world, but it was not generated there: from above, from heaven, it was planted in the world as a supernatural realm of grace. Therefore its existence and its extension is in no wise dependent on worldly power; its foundations lie deeper, in the principle of truth which has entered the world with Christ. For this cause came he into the world, that he should bear witness unto the truth. All they that are of the truth, do him homage as their king, and hear his kingly voice. The same principle works in them as that of a new worship; they worship the Father in spirit and in truth.
But this elevated sense of truth in individual souls is the fruit of a higher form of being. He that is of God heareth the words of God; but they hear them not who are not of God. The entrance into the kingdom of God therefore necessarily presupposes a new beginning of man's life, a new birth of water and of the Spirit. Wherever the kingdom of God obtains a foothold, it assumes the form of an entirely new state of things, of a new creation, of the principle of a new mental activity, a new nature of the spirit.
A transmutation of our souls, such as just described, necessarily involves a rupture with the natural man, a discarding of the original individuality. Without this alteration we are impervious to the new light which is to enter our souls together with the kingdom of God. This indispensable self-denial is accomplished by a two-fold instrumentality—by the love of God, which is the first commandment, and by the love of our neighbor as ourselves. Whoever is in this frame of mind is pronounced by Jesus to be not far from the kingdom of God.
What has been said reveals another peculiarity of the kingdom of God on earth. It is a supernatural kingdom. At this point only do we fully comprehend the title of the Church to [{673}] the designation of the kingdom of heaven. The kingdom of God historically manifested in the Church is intimately connected with the intro-divine relations or the inmost life of the Deity. By admission into the Church God the Father translates us into the kingdom of his beloved Son. This is not merely an exercise of the creative love common to the three persons of the Trinity. On the contrary, it is an evidence what manner of love the Father hath bestowed upon us that we should be called the sons of God. Precisely in this is the peculiar supernatural character of this dispensation made manifest. It is this supernatural characteristic of the Church which accounts for the bestowal upon the Church of the name of the coming realm of glory. The germ of the latter is already contained in the existing Church. While, for this reason, the Church visible is called the kingdom of heaven, so the latter continues to bear the name of the Church even in the splendor of its eternal glory. This circumstance warrants the bold utterance of the apostle that our conversation is in heaven. In the same sense it is laid down in the catechism of the council of Trent that the Church militant and the Church triumphant are but two parts of the one Church, not two churches; and with entire consistency the same authority speaks of the Church militant as synonymous with the kingdom of heaven.
It is but another expression for the supernatural character of the Church if she is called the Jerusalem which is above, even in her historical form and figure. And precisely because this epithet applies to her, she is free and is our mother. The catholicity of the Church, her faculty of enfolding all mankind, of being the spiritual mother of us all, is owing to her supernatural character.
This doctrine of the supernaturalness of the Church is the connecting link between the essence and the form of Catholicism. As the latter is supernatural in its character, so must the form of its establishment bear a supernatural impress. How can anything utterly supernatural attain an adequate form of expression by mere natural development? It assumes a historical reality in so far only as it assumes simultaneously with its supernatural essence a corresponding supernatural image. The form as well as the substance of the Church must needs be the fruit of an immediate interposition of God, because the substance must needs exercise its supernatural functions.