"The Holy Ghost is said to be the bond of the Father and Son, inasmuch as He is Love; because, since the Father loves Himself and the Son with one Love, and conversely, there is expressed in the Holy Ghost, as Love, the relation of the Father to the Son, and conversely, as that of the lover to the beloved. But from the fact that the Father and the Son mutually love one another, it necessarily follows that this mutual Love, the Holy Ghost, proceeds from both. As regards origin, therefore, the Holy Ghost is not the medium, but the third person in the Trinity; whereas as regards the aforesaid relation He is the bond between the two persons, as proceeding from both."
~St. Thomas Aquinas: "Summa Theologica," I, q. 37, a. 1, ad 3.
~St. Thomas Aquinas: "Summa Theologica," I, q. 37, a. 1, ad 3.
