But they deride our state of nature, and din into our ears the manner of our being born, supposing in this way to make the mystery ridiculous, as if it were unbecoming in God by such an entrance into the world as this to connect Himself with the fellowship of the human life. But we touched upon this point before, when we said that the only thing which is essentially degraded is moral evil or whatever has an affinity with such evil; whereas the orderly process of Nature, arranged as it has been by the Divine will and law, is beyond the reach of any misrepresentation on the score of wickedness: otherwise this accusation would reach up to the Author of Nature, if anything connected with Nature were to be found fault with as degraded and unseemly.
If, then, the Deity is separate only from evil, and if there is no nature in evil, and if the mystery declares that God was born in man but not in evil; and if, for man, there is but one way of entrance upon life, namely that by which the embryo passes on to the stage of life, what other mode of entrance upon life would they prescribe for God? These people, I mean, who, while they judge it right and proper that the nature which evil had weakened should be visited by the Divine power, yet take offense at this special method of the visitation, not remembering that the whole organization of the body is of equal value throughout, and that nothing in it, of all the elements that contribute to the continuance of the animal life, is liable to the charge of being worthless or wicked.
For the whole arrangement of the bodily organs and limbs has been constructed with one end in view, and that is, the continuance in life of humanity; and while the other organs of the body conserve the present actual vitality of men, each being apportioned to a different operation, and by their means the faculties of sense and action are exercised, the generative organs on the contrary involve a forecast of the future, introducing as they do, by themselves, their counteracting transmission for our race.
Looking, therefore, to their utility, to which of those parts which are deemed more honourable are these inferior? Nay, than which must they not in all reason be deemed more worthy of honour? For not by the eye, or ear, or tongue, or any other sense, is the continuation of our race carried on. These, as has been remarked, pertain to the enjoyment of the present. But by those other organs the immortality of humanity is secured, so that death, though ever operating against us, thus in a certain measure becomes powerless and ineffectual, since Nature, to baffle him, is ever as it were throwing herself into the breach through those who come successively into being.
What unseemliness, then, is contained in our revelation of God mingled with the life of humanity through those very means by which Nature carries on the combat against death?
Source: The Great Catechism (New Advent)