t's body was conceived of (_de_) the Holy Ghost.

Obj. 3: Further, no one thing is made of two, except they be in some
way mingled. But Christ's body was formed of (_de_) the Virgin Mary.
If therefore we say that Christ was conceived of (_de_) the Holy
Ghost, it seems that a mingling took place of the Holy Ghost with the
matter supplied by the Virgin: and this is clearly false. Therefore
we should not say that Christ was conceived of (_de_) the Holy Ghost.

_On the contrary,_ It is written (Matt. 1:18): "Before they came
together, she was found with child, of (_de_) the Holy Ghost."

_I answer that,_ Conception is not attributed to Christ's body alone,
but also to Christ Himself by reason of His body. Now, in the Holy
Ghost we may observe a twofold habitude to Christ. For to the Son of
God Himself, who is said to have been conceived, He has a habitude of
consubstantiality: while to His body He has the habitude of efficient
cause. And this preposition of (_de_) signifies both habitudes: thus
we say that a certain man is "of (_de_) his father." And therefore we
can fittingly say that Christ was conceived of the Holy Ghost in such
a way that the efficiency of the Holy Ghost be referred to the body
assumed, and the consubstantiality to the Person assuming.

Reply Obj. 1: Christ's body, through not being consubstantial with
the Holy Ghost, cannot properly be said to be conceived "of" (_de_)
the Holy Ghost, but rather "from (_ex_) the Holy Ghost," as Ambrose
says (De Spir. Sanct. ii.): "What is from someone is either from his
substance or from his power: from his substance, as the Son who is
from the Father; from his power, as all things are from God, just as
Mary conceived from the Holy Ghost."

Reply Obj. 2: It seems that on this point there is a difference of
opinion between Jerome and certain other Doctors, who assert that the
Holy Ghost took the place of seed in this conception. For Chrysostom
says (Hom. i in Matth. [*Opus Imperf., among the supposititious
writings]): "When God's Only-Begotten was about to enter into the
Virgin, the Holy Ghost preceded Him; that by the previous entrance of
the Holy Ghost, Christ might be born unto sanctification according to
His body, the Godhead entering instead of the seed." And Damascene
says (De Fide Orth. iii): "God's wisdom and power overshadowed her,
like unto a Divine seed."

But these expressions are easily explained. Because Chrysostom and
Damascene compare the Holy Ghost