Important Questions about the Conception of Christ in the Womb of the Virgin Mary

Question: Why is the conception of Christ attributed to the Holy Spirit in particular?

Answer: First of all, this was for the purpose of a holy conception. The mass out of which Christ was conceived, needed to have been a sanctified mass, and pure from all stain of sin. And since sanctification is particularly the work of the Holy Spirit (Romans 1:4), therefore is the Holy Spirit said to have effected the work of Christ's conception in the womb of the blessed Virgin. 

Second, it is befitting on the part of the human nature, which was assumed, that it be attributed to the Holy Spirit. We are then to understand that human nature was assumed into the unity of Person, not because of merits, but because of grace, which is attributed to the Holy Spirit (1 Corinthians 12:4). St. Augustine said "For it was by this grace that a man, without any antecedent merit, was at the very commencement of His existence as man, so united in one person with the Word of God, that the very person who was Son of man was at the same time Son of God, and the very person who was Son of God was at the same time Son of man;" (The Enchiridion, Chapter 40).

The Holy Spirit here does not act materially, but rather efficiently, so that Christ was conceived from the power of the Spirit, but not from the substance of the Spirit, not by generation, but by blessing and consecration. In brief, Christ was conceived from the power of the Spirit, not the Spirit's substance.

The Holy Spirit's action of effecting the conception of Christ may be referred to in three heads - 1) the immediate work wherein the Spirit gave the Virgin the ability to conceive apart from intercourse; 2) the work of consecration in which the Spirit sanctified that mass from which the body of the Son of God was formed, cleansing it from sin; 3) the uniting of the divine and human natures in the single Person. 

“After the assent of the holy Virgin, the Holy Spirit came down upon her and purified her, giving her the power to receive the divinity of the Word and the power to procreate.” (John Damascene, Exposition of the Orthodox Faith, Book III, Chapter 2)

Question: Can the Holy Spirit then be called the father of Christ, since he effected the work of Christ's conception?

Answer: No, because, as was stated above, the flesh of Christ was not begotten from the substance of the Holy Spirit, but from the substance of the Virgin Mary. 

To say that Christ was begotten from the substance of the Holy Spirit  would lead to Eutychianism, inasmuch as the Holy Spirit, like each of the divine persons, possesses the divine essence, thus the human nature would be of the substance of the divine essence, which is a plain contradiction.

"For that which is of [ex] any one is either of his substance or of his power. Of his substance, as the Son, Who says: I came forth of the Mouth of the Most High; Sirach 24:3 as the Spirit, Who proceeds from the Father; John 15:20 of Whom the Son says: He shall glorify Me, for He shall receive of Mine. John 16:14 But of the power, as in the passage: One God the Father, of Whom are all things. How, then, was Mary with child of the Holy Spirit? If as of her substance, was the Spirit, then, changed into flesh and bones? Certainly not. But if the Virgin conceived as of His operation and power, who can deny that the Holy Spirit is Creator?" (Ambrose, On the Holy Spirit, Book II, Chapter 5)

Question: Was the body of Christ formed in the womb of the Virgin in a moment or successively?

Answer: Three things occur in this act of the Holy Spirit:

[1]. The preparation of the material (or "mass") from which the body of Christ was formed.

[2]. The formation of the body from the material that was prepared.

[3]. The perfection of the same body brought to a "just quantity" by its own increase, little by little. 

Gregory the Great and Thomas Aquinas believed that the body of Christ was formed in the womb of the Virgin in an instant, whereas the Reformed church (with exception of Jerome Zanchius) has historically taught that the body of Christ was formed by succession, rather than instantaneously, as part of preserving the true humanity of Christ. 

First of all, I would concur with Johann Gerhard (one of the Lutheran scholastics), that we must distinguish between the formation of the members and the increase of the formed members. The former occurred in an instant moment, but the latter was successive in time. 

The following position I take to be the most safe middle ground in this debate amongst theologians concerning the gestation of Christ:

“In the very womb of the mother there was a growing of the mass and of the quantity of the body and members of our Lord over a period of days, just as also after His birth, so that those which at first were smaller then, through the coming of nourishment, gradually became larger. Nevertheless the formation of the parts according to shape and distinction happened at the very first moment of the sacred conception, and this was perfected by the power of the Holy Spirit, the accomplisher of this work.” (cited in Johann Gerhard, Theological Commonplaces - On Christ, pg. 108)