We would say, moreover, that death ceases in the world when the sin of the world dies, referring the saying to the mystical words of the apostle, which run as follows: “When He shall have put all enemies under His feet, then the last enemy that shall be destroyed is death.” And also: “When this corruptible shall have put on incorruption, then shall be brought to pass the saying that is written, Death is swallowed up in victory.” The “strait descent,” again, may perhaps be referred by those who hold the doctrine of transmigration of souls to that view of things.
And it is not incredible that the gates which are said to open spontaneously are referred obscurely by some to the words, “Open to me the gates of righteousness, that I may go into them, and praise the Lord; this gate of the Lord, into it the righteous shall enter;” and again, to what is said in the ninth psalm, “You that liftest me up from the gates of death, that I may show forth all Your praise in the gates of the daughter of Zion.” The Scripture further gives the name of “gates of death” to those sins which lead to destruction, as it terms, on the contrary, good actions the “gates of Zion.”
So also “the gates of righteousness,” which is an equivalent expression to “the gates of virtue,” and these are ready to be opened to him who follows after virtuous pursuits. The subject of the “tree of life” will be more appropriately explained when we interpret the statements in the book of Genesis regarding the paradise planted by God. Celsus, moreover, has often mocked at the subject of a resurrection,— a doctrine which he did not comprehend; and on the present occasion, not satisfied with what he has formerly said, he adds, “And there is said to be a resurrection of the flesh by means of the tree;” not understanding, I think, the symbolic expression, that “through the tree came death, and through the tree comes life,” because death was in Adam, and life in Christ.
He next scoffs at the “tree,” assailing it on two grounds, and saying, “For this reason is the tree introduced, either because our teacher was nailed to a cross, or because he was a carpenter by trade;” not observing that the tree of life is mentioned in the Mosaic writings, and being blind also to this, that in none of the Gospels current in the Churches is Jesus Himself ever described as being a carpenter.
Source: Against Celsus (New Advent)