A still more cogent argument can be derived from 1 Cor. III, 6 sq.: “I have planted, Apollo watered, but God gave the increase. Therefore, neither he that planteth is anything, nor he that watereth; but God that giveth the increase.”(47) In this beautiful allegory the Apostle compares the genesis of supernatural faith in the soul to that of a plant under the care of a gardener, who while he plants and waters, yet looks to God for “the increase.” The Apostle and his disciple Apollo are the spiritual gardeners through whose preaching the Corinthians received the grace of mediate illumination. But, as St. Paul says, this preaching would have been useless (_non est aliquid_) had not God given “the increase.” In other words, the grace of immediate illumination was necessary to make the Apostolic preaching effective. “For,” in the words of St. Augustine, “God Himself contributes to the production of fruit in good trees, when He both externally waters and tends them by the agency of His servants, and internally by Himself also gives the increase.”(48) β) The argument from Tradition is based chiefly on St. Augustine, “the Doctor of Grace,” whose authority in this branch of dogmatic theology is unique.(49) His writings abound in many such synonymous terms for the grace of immediate illumination, as _cogitatio pia, vocatio alta et secreta, locutio in cogitatione, aperitio veritatis_, etc., etc. He says among other things: “Instruction and admonition are external aids, but he who controls the hearts has his cathedra in heaven.”(50) Augustine esteems human preaching as nothing and ascribes all its good effects to grace. “It is the internal Master who teaches; Christ teaches and His inspiration.”(51) In harmony with his master, St. Fulgentius of Ruspe, the ablest defender of the Augustinian (_i.e._ Catholic) doctrine of grace, says: “In vain will our sacred discourses strike the external ear, unless God by a spiritual gift opens the hearing of the interior man.”(52) 2. THE STRENGTHENING GRACE OF THE WILL.—This grace, usually called _gratia inspirationis_,(53) may also be either mediate or immediate, according as pious affections and wholesome resolutions are produced in the soul by a preceding illumination of the intellect or directly by the Holy Ghost. Owing to the psychological interaction of intellect and will, every grace of the mind, whether mediate or immediate, is _eo ipso_ also a mediate grace of the will, which implies a new act of the soul, but not a new grace. What we are concerned with here is the immediate strengthening grace of the will, which is far more important and more necessary. We are not able to demonstrate this teaching from Sacred Scripture. The texts John VI, 44 and Phil. II, 13, which are usually adduced in this connection, are inconclusive.