PROCESSION OF THE HOLY GHOST FROM THE FATHER AND THE SON
We should recall that the act of understanding proceeds from the intellectual power of the mind. When the intellect actually understands, the object it understands is in it. The presence of the object known in the knower results from the intellectual power of the mind, and is its word, as we said above. Likewise, what is loved is in the lover, when it is actually loved. The fact that an object is actually loved, results from the lover's power to love and from the lovable good as actually known. Accordingly the presence of the beloved object in the lover is brought about by two factors: the appetitive principle and the intelligible object as apprehended, that is, the word conceived about the lovable object. Therefore, since the Word in God who knows and loves Himself is the Son, and since He to whom the Word belongs is the Father of the Word, as is clear from our exposition, the necessary consequence is that the Holy Spirit, who pertains to the love whereby God is in Himself as beloved in lover, proceeds from the Father and the Son. And so we say in the Creed: "Who proceeds from the Father and the Son."