The following is an excerpt from "The Grand Miracle," a chapter in C.S. Lewis' book Miracles.
In the Christian story God descends to reascend. He comes down; down from the heights of absolute being into time and space, down into humanity; down further still, if embryologists are right, to recapitulate in the womb ancient and pre-human phases of life; down to the very roots and seabed of the Nature He created. But he goes down to come up again and bring the whole ruined world up with Him. One has the picture of a strong man stooping lower and lower to get himself underneath some great complicated burden. He must stoop in order to lift; he must almost disappear under the load before he incredibly straightens his back and marches off with the whole mass swaying on his shoulders.
Or one may think of a diver, first reducing himself to nakedness, then glancing in mid-air, then gone with a splash, vanished, rushing down through green and warm water into black and cold water, down through increasing pressure into the death-like region of ooze and slime and old decay; then up again, back to color and light, his lungs almost bursting, till suddenly he breaks surface again, holding in his hand the dripping, precious thing that he went down to recover. He and it are both colored now that they have come up into the light; down below, where it lay colorless in the dark, he lost his color too.
In this descent to reascent everyone will recognize a familiar pattern: a thing written all over the world. It is the pattern of vegetable life. It must belittle itself into something hard, small and deathlike. It must fall into the ground; thence the new life reascends. It is the pattern of all animal generation too. There is a descent from the full and perfect organisms into the spermatozoon and ovum, and in the dark womb a life at first inferior in kind to that of the species which is being reproduced; then the slow ascent to the perfect embryo, to the living, conscious baby, and finally to the adult. So it is also in our moral and emotional life. The first innocent and spontaneous desires have to submit to the deathlike process of control or total denial; but from that there is a reascent to fully formed character in which the strength of the original material all operates but in a new way. Death and Rebirth--go down to go up--it is a key principle. Through this bottleneck, this belittlement, the highroad nearly always lies.
The doctrine of the Incarnation, if accepted, puts this principle even more emphatically at the center. The pattern is there in Nature because it was first there in God. All the instances of it which I have mentioned turn out to be but transpositions of the Divine theme into a minor key. I am not now referring simply to the Crucifixion and Resurrection of Christ. The total pattern, of which they are only the turning point, is the real Death and Rebirth; for certainly no seed ever fell from so fair a tree into so dark and cold a soil as would furnish more than a faint analogy to this huge descent and reascension in which God dredged the salt and oozy bottom of Creation.