At the beginning of life in the natural order is an act of substitution and co-inherence. A man can have no child unless his seed is received and carried by a woman; a woman can have no child unless she receives and carries the seed of a man–literally bearing the burden. It is not only a mutual act; it is a mutual act of substitution. The child itself for nine months literally co-inheres in its mother; there is no human creature that has not sprung from such a period of such an interior growth.
In that natural co-inherence the Christian church has understood another; the about-to-be-born already co-inheres in an ancestral and contemporary guilt. It is shapen in wickedness, and in sin has its mother conceived it (Ps. 51:5). The fundamental fact of itself is already opposed to the principle of the universe; it knows that good as evil, and therefore it derives and desires its own good disorderly. It has been sown in corruption, and in corruption it emerges into separate life.
It has been the habit of the church to baptize it, as soon as it has emerged, by the formula of the Trinity-in-Unity. As it passes from the most material co-inherence it is received into the supernatural; and it is received by a deliberate act. The godparents present themselves as its substitutes; by their intentions and their belief (and they are there to present even for “those of riper years") the newborn is granted “that which by nature he cannot have,” he is “incorporated” into the church, he is made “partaker” of death and resurrection. It is this co-inherence which, at the confirmation, he himself confesses and ratifies.
The faith into which he is received has declared that principle to be the root and the pattern of the supernatural as of the natural world. And the faith is the only body to have done so. It has proclaimed that this is due to the deliberate choice and operation of the divine Word. Had he willed, he could presumably have raised for his Incarnation a body in some other way than he chose. But he preferred to shape himself within the womb, to become hereditary, to owe to humanity the flesh he divinitized by the same principle–"not by conversion of the Godhead into flesh, but by taking of the manhood into God.” By an act of substitution he reconciled the natural world with the world of the kingdom of heaven, sensuality with substance. He restored substitution and co-inherence everywhere; up and down the ladder of that great substitution all our lesser co-inherences cohere. And when the Christian Church desired to define the nature of the Alone, she found no other term; It mutually co-inheres by Its own nature. The triune formula by which the child is baptized is precisely the incomprehensible formula of this.