The Holy Ghost appeared over Christ at His baptism, under the form of a dove, for four reasons. First, on account of the disposition required in the one baptized--namely, that he approach in good faith: since! as it is written (Wisdom 1:5): "The holy spirit of discipline will flee from the deceitful." For the dove is an animal of a simple character, void of cunning and deceit: whence it is said (Matthew 10:16): "Be ye simple as doves."

Secondly, in order to designate the seven gifts of the Holy Ghost, which are signified by the properties of the dove. For the dove dwells beside the running stream, in order that, on perceiving the hawk, it may plunge in and escape. This refers to the gift of wisdom, whereby the saints dwell beside the running waters of Holy Scripture, in order to escape the assaults of the devil. Again, the dove prefers the more choice seeds. This refers to the gift of knowledge, whereby the saints make choice of sound doctrines, with which they nourish themselves. Further, the dove feeds the brood of other birds. This refers to the gift of counsel, with which the saints, by teaching and example, feed men who have been the brood, i.e. imitators, of the devil. Again, the dove tears not with its beak. This refers to the gift of understanding, wherewith the saints do not rend sound doctrines, as heretics do. Again, the dove has no gall. This refers to the gift of piety, by reason of which the saints are free from unreasonable anger. Again, the dove builds its nest in the cleft of a rock. This refers to the gift of fortitude, wherewith the saints build their nest, i.e. take refuge and hope, in the death wounds of Christ, who is the Rock of strength. Lastly, the dove has a plaintive song. This refers to the gift of fear, wherewith the saints delight in bewailing sins.

Thirdly, the Holy Ghost appeared under the form of a dove on account of the proper effect of baptism, which is the remission of sins and reconciliation with God: for the dove is a gentle creature. Wherefore, as Chrysostom says, (Hom. xii in Matth.), "at the Deluge this creature appeared bearing an olive branch, and publishing the tidings of the universal peace of the whole world: and now again the dove appears at the baptism, pointing to our Deliverer."

Fourthly, the Holy Ghost appeared over our Lord at His baptism in the form of a dove, in order to designate the common effect of baptism--namely, the building up of the unity of the Church. Hence it is written (Ephesians 5:25-27): "Christ delivered Himself up . . . that He might present . . . to Himself a glorious Church, not having spot or wrinkle, or any such thing . . . cleansing it by the laver of water in the word of life." Therefore it was fitting that the Holy Ghost should appear at the baptism under the form of a dove, which is a creature both loving and gregarious. Wherefore also it is said of the Church (Canticles 6:8): "One is my dove."

But on the apostles the Holy Ghost descended under the form of fire, for two reasons. First, to show with what fervor their hearts were to be moved, so as to preach Christ everywhere, though surrounded by opposition. And therefore He appeared as a fiery tongue. Hence Augustine says (Super Joan., Tract. vi): Our Lord "manifests" the Holy Ghost "visibly in two ways"--namely, "by the dove corning upon the Lord when He was baptized; by fire, coming upon the disciples when they were met together . . . In the former case simplicity is shown, in the latter fervor . . . We learn, then, from the dove, that those who are sanctified by the Spirit should be without guile: and from the fire, that their simplicity should not be left to wax cold. Nor let it disturb anyone that the tongues were cloven . . . in the dove recognize unity."

Secondly, because, as Chrysostom says (Gregory, Hom. xxx in Ev.): "Since sins had to be forgiven," which is effected in baptism, "meekness was required"; this is shown by the dove: "but when we have obtained grace we must look forward to be judged"; and this is signified by the fire.