Objection 3: Further, death is a kind of corruption. But what is corrupted by substantial corruption after being corrupted, exists no longer, since corruption is change from being to non-being. Therefore, Christ's body, after it was dead, did not remain identically the same, because death is a substantial corruption.
On the contrary, Athanasius says (Epist. ad Epict.): "In that body which was circumcised and carried, which ate, and toiled, and was nailed on the tree, there was the impassible and incorporeal Word of God: the same was laid in the tomb." But Christ's living body was circumcised and nailed on the tree; and Christ's dead body was laid in the tomb. Therefore it was the same body living and dead.
I answer that, The expression "simply" can be taken in two senses. In the first instance by taking "simply" to be the same as "absolutely"; thus "that is said simply which is said without addition," as the Philosopher put it (Topic. ii): and in this way the dead and living body of Christ was simply identically the same: since a thing is said to be "simply" identically the same from the identity of the subject. But Christ's body living and dead was identical in its suppositum because alive and dead it had none other besides the Word of God, as was stated above (A[2]). And it is in this sense that Athanasius is speaking in the passage quoted.
In another way "simply" is the same as "altogether" or "totally": in which sense the body of Christ, dead and alive, was not "simply" the same identically, because it was not "totally" the same, since life is of the essence of a living body; for it is an essential and not an accidental predicate: hence it follows that a body which ceases to be living does not remain totally the same. Moreover, if it were to be said that Christ's dead body did continue "totally" the same, it would follow that it was not corrupted---I mean, by the corruption of death: which is the heresy of the Gaianites, as Isidore says (Etym. viii), and is to be found in the Decretals (xxiv, qu. iii). And Damascene says (De Fide Orth. iii) that "the term 'corruption' denotes two things: in one way it is the separation of the soul from the body and other things of the sort; in another way, the complete dissolving into elements. Consequently it is impious to say with Julian and Gaian that the Lord's body was incorruptible after the first manner of corruption before the resurrection: because Christ's body would not be consubstantial with us, nor truly dead, nor would we have been saved in very truth. But in the second way Christ's body was incorrupt."
Reply to Objection 1: The dead body of everyone else does not continue united to an abiding hypostasis, as Christ's dead body did; consequently the dead body of everyone else is not the same "simply," but only in some respect: because it is the same as to its matter, but not the same as to its form. But Christ's body remains the same simply, on account of the identity of the suppositum, as stated above.
Reply to Objection 2: Since a thing is said to be the same identically according to suppositum, but the same specifically according to form: wherever the suppositum subsists in only one nature, it follows of necessity that when the unity of species is taken away the unity of identity is also taken away. But the hypostasis of the Word of God subsists in two natures; and consequently, although in others the body does not remain the same according to the species of human nature, still it continues identically the same in Christ according to the suppositum of the Word of God.
Reply to Objection 3: Corruption and death do not belong to Christ by reason of the suppositum, from which suppositum follows the unity of identity; but by reason of the human nature, according to which is found the difference of death and of life in Christ's body.
Whether Christ's death conduced in any way to our salvation?
Objection 1: It would seem that Christ's death did not conduce in any way to our salvation. For death is a sort of privation, since it is the privation of life. But privation has not any power of activity, because it is nothing positive. Therefore it could not work anything for our salvation.
Objection 2: Further, Christ's Passion wrought our salvation by way of merit. But Christ's death could not operate in this way, because in death the body is separated from the soul, which is the principle of meriting. Consequently, Christ's death did not accomplish anything towards our salvation.
Objection 3: Further, what is corporeal is not the cause of what is spiritual. But Christ's death was corporeal. Therefore it could not be the cause of our salvation, which is something spiritual.
On the contrary, Augustine says (De Trin. iv): "The one death of our Saviour," namely, that of the body, "saved us from our two deaths," that is, of the soul and the body.
I answer that, We may speak of Christ's death in two ways, "in becoming" and "in fact." Death is said to be "in becoming" when anyone from natural or enforced suffering is tending towards death: and in this way it is the same thing to speak of Christ's death as of His Passion: so that in this sense Christ's death is the cause of our salvation, according to what has been already said of the Passion (Q[48]). But death is considered in fact, inasmuch as the separation of soul and body has already taken place: and it is in this sense that we are now speaking of Christ's death. In this way Christ's death cannot be the cause of our salvation by way of merit, but only by way of causality, that is to say, inasmuch as the Godhead was not separated from Christ's flesh by death; and therefore, whatever befell Christ's flesh, even when the soul was departed, was conducive to salvation in virtue of the Godhead united. But the effect of any cause is properly estimated according to its resemblance to the cause. Consequently, since death is a kind of privation of one's own life, the effect of Christ's death is considered in relation to the removal of the obstacles to our salvation: and these are the death of the soul and of the body. Hence Christ's death is said to have destroyed in us both the death of the soul, caused by sin, according to Rom. 4:25 : "He was delivered up [namely unto death] for our sins": and the death of the body, consisting in the separation of the soul, according to 1 Cor. 15:54 : "Death is swallowed up in victory."
Reply to Objection 1: Christ's death wrought our salvation from the power of the Godhead united, and not consisted merely as His death.
Reply to Objection 2: Though Christ's death, considered "in fact" did not effect our salvation by way of merit, yet it did so by way of causality, as stated above.
Reply to Objection 3: Christ's death was indeed corporeal; but the body was the instrument of the Godhead united to Him, working by Its power, although dead.