Father Cassilly discusses the doctrine of appropriation, which helps the human mind begin to understand the nature and activity of God.
He notes: “Reflective minds may be moved to ask the question, why, then, the indwelling in the just soul and its sanctification, which are equally of the Three Divine Persons, are attributed so prominently to the Third Person, as though they were His peculiar office. A sufficient answer to this difficulty will be to recall the doctrine of the schools, that, in our mind, certain manifestations of the Godhead in creatures are closely allied with the incommunicable personality of one or other of the Divine Persons. Hence, by what is called ‘appropriation,’ we appropriate or ascribe to one Person what actually belongs to the Three.”
“Thus, to the Father the work of creation and whatever involves a striking display of power are often imputed, since with the notion of unbegotten and unproduced, the idea of power and omnipotence is closely connected. To the Son, who is the Eternal Word begotten by knowledge, works of knowledge and wisdom such as the order of the universe are referred. To the Holy Ghost, Who is the Substantial Love of Father and Son, we attribute special manifestations of love and goodness. From this we can understand how the sanctification of the soul, though pertaining alike to the Three Divine Persons, comes to be appropriated to the Holy Spirit, for it is preeminently a work of love and goodness.”
“The Father, Son and Holy Ghost, then, come with power, wisdom and love to sanctify us, to take up Their abode within us as friend to friend, and give us some accidental share and participation, as much as we have capacity for, in Their Substantial Love and Sanctity. This is the mission of the Holy Ghost to the just soul.”
Quotations from Francis Cassilly, A Story of Love, 2d ed. (St. Louis: B. Herder, 1917).