Thomas Aquinas

“ It would seem that the Holy Ghost should be called Christ's father in respect of His humanity. Because, according to the Philosopher (De Gener. Animal. i) : "The Father is the active principle in generation, the Mother supplies the matter." But the Blessed Virgin is called Christ's Mother, by reason of the matter which she supplied in His conception. Therefore it seems that the Holy Ghost can be called His father, through being the active principle in His conception. ”

“ Because a transformation is said to be natural by reason not only of an active but also of a passive intrinsic principle: for the Philosopher says expressly (Phys. viii) that in heavy and light things there is a passive, and not an active, principle of natural movement. Nor is it possible for matter to be active in its own formation, since it is not in act. ”

“ The generative power of the female is imperfect compared to that of the male. And, therefore, just as in the arts the inferior art gives a disposition to the matter to which the higher art gives the form, as is stated Phys. ii, so also the generative power of the female prepares the matter, which is then fashioned by the active power of the male.
Reply to Objection 3: In order for a transformation to be natural, there is no need for an active principle in matter, but only for a passive principle, as stated above. ”

“ I answer that, Some say that the Blessed Virgin cooperated actively in Christ's conception, both by natural and by a supernatural power. By natural power, because they hold that in all natural matter there is an active principle. otherwise they believe that there would be no such thing as natural transformation. ”

“ For the term of the Incarnation was that that man, who was being conceived, should be the Holy one and the Son of God. Now, both of these are attributed to the Holy Ghost. For by Him men are made to be sons of God, according to Gal. ”

“ Secondly, this is befitting to the cause of the Incarnation, on the part of the nature assumed. Because we are thus given to understand that human nature was assumed by the Son of God into the unity of Person, not by reason of its merits, but through grace alone ”

“ Nor, again, is it possible for anything to put itself in motion except it be divided into two parts, one being the mover, the other being moved: which happens in animate things only, as is proved Phys. ”