Chapter 46 — That love in God is called the Spirit

Since the object known is in the knower, and the beloved is in the lover, the different ways of existing in something must be considered in both cases before us. Since the act of understanding takes place by a certain assimilation of the knower to the object known, the object known must be in the knower according as a likeness of it is present in him. But the act of loving takes place through the lover’s being moved in a certain way by the beloved, for the beloved draws the lover to himself. Accordingly, the act of loving does not reach its perfection in a likeness of the beloved, as the act of understanding reaches perfection in a likeness of the object understood, but rather reaches its perfection in a drawing of the lover to the beloved himself.

The bestowal of a likeness is principally effected by univocal generation, in accord with which, among living beings, the begetter is called father and the begotten is called son. Among such things, the first motion occurs according to a spirit. Therefore, as within the Godhead the way whereby God is in God as the known in the knower is expressed by our calling the Word of God ‘Son’, so we express the way by which God is in God as the beloved is in the lover by acknowledging a Spirit in God, who is the love of God. And this is why, according to the rule of Catholic faith, we are directed to believe in the Spirit.