[quote="PacoG, post:1, topic:319099"]
At the Transfiguration, was the Lord appearing in His glorified body? Was it a foretaste of the Resurrection?
How about Elijah and Moses?
My guess is that Jesus was still God, the Second Person of the Trinity. All that was still in his powers...He could transfigure and he could converse with the Holy Souls in the Bussom of Abraham.
St. Thomas Aquinas writes about this in the Summa (question 45):
Our Lord, after foretelling His Passion to His disciples, had exhorted them to follow the path of His sufferings (Matthew 16:21-24). Now in order that anyone go straight along a road, he must have some knowledge of the end: thus an archer will not shoot the arrow straight unless he first see the target. Hence Thomas said (John 14:5): "Lord, we know not whither Thou goest; and how can we know the way?" Above all is this necessary when hard and rough is the road, heavy the going, but delightful the end.
Now by His Passion Christ achieved glory, not only of His soul, not only of His soul, which He had from the first moment of His conception, but also of His body ...] To which glory He brings those who follow the footsteps of His Passion, according to Acts 14:21: "Through many tribulations we must enter into the kingdom of God." Therefore it was fitting that He should show His disciples the glory of His clarity (which is to be transfigured), to which He will configure those who are His; according to Philippians 3:21: "(Who) will reform the body of our lowness configured [Douay: 'made like'] to the body of His glory."
Hence Bede says on Mark 8:39: "By His loving foresight He allowed them to taste for a short time the contemplation of eternal joy, so that they might bear persecution bravely."
As Jerome says on Matthew 17:2: "Let no one suppose that Christ," through being said to be transfigured, "laid aside His natural shape and countenance, or substituted an imaginary or aerial body for His real body. The Evangelist describes the manner of His transfiguration when he says: 'His face did shine as the sun, and His garments became white as snow.' Brightness of face and whiteness of garments argue not a change of substance, but a putting on of glory."
The clarity which Christ assumed in His transfiguration was the clarity of glory as to its essence, but not as to its mode of being. For the clarity of the glorified body is derived from that of the soul, as Augustine says (Ep. ad Diosc. cxviii).
And in like manner the clarity of Christ's body in His transfiguration was derived from His God. head, as Damascene says (Orat. de Transfig.) and from the glory of His soul.
That the glory of His soul did not overflow into His body from the first moment of Christ's conception was due to a certain Divine dispensation, that, as stated above (14, 1, ad 2), He might fulfil the mysteries of our redemption in a passible body.
This did not, however, deprive Christ of His power of outpouring the glory of His soul into His body. And this He did, as to clarity, in His transfiguration, but otherwise than in a glorified body.
For the clarity of the soul overflows into a glorified body, by way of a permanent quality affecting the body. Hence bodily refulgence is not miraculous in a glorified body. But in Christ's transfiguration clarity overflowed from His Godhead and from His soul into His body, not as an immanent quality affecting His very body, but rather after the manner of a transient passion, as when the air is lit up by the sun. Consequently the refulgence, which appeared in Christ's body then, was miraculous: just as was the fact of His walking on the waves of the sea.
Hence Dionysius says (Ep. ad Cai. iv): "Christ excelled man in doing that which is proper to man: this is shown in His supernatural conception of a virgin and in the unstable waters bearing the weight of material and earthly feet."
Also, about Moses and Elijah, a quote from Catholic Answers Apologist Peggy Frye:
The appearance at the Transfiguration of Moses and Elijah (symbolizing the law and the prophets) was to announce the fulfillment of the Old Covenant through Christ's death on the cross (Jn 1:17; CCC 554-555).
...] Elijah never died (2 Kgs 2:11) [and] there are also hints in the Church Fathers that Moses' body was reunited with his soul in heaven after his death.
While God can allow saints and angels to take the form of human bodies, this doesn't mean that Moses and Elijah actually appeared here in their physical bodies.This episode tells us only that they were somehow manifested to Peter, James, and John. It does not explain the mode of manifestation.
Hope that helps :)