Works of St. Anselm, tr. by Sidney Norton Deane, [1903], at sacred-texts.com
This love is uncreated and creator, as are Father and Son; and yet it is with them not three, but one uncreated and creative being. And it may be called the Spirit of Father and Son.
BUT, since this love separately is the supreme Being, as are Father and Son, and yet at once Father and Son, and the love of both are not more than one, but one supreme Being, which alone was created by none, and created all things through no other than itseIf; since this is true, necessarily, as the Father separately, and the Son separately, are each uncreated and creator, so, too, love separately is uncreated and creator, and yet all three at once are not more than one, but one uncreated and creative being.
None, therefore, makes or begets or creates the Father, but the Father alone begets, but does not create, the Son; while Father and Son alike do not create or beget, but somehow, if such an expression may be used, breathe their love: for, although the supremely immutable Being does not breathe after our fashion, yet the truth that this Being sends forth this, its love, which proceeds from it, not by departing from it, but by deriving existence from it, can perhaps be no better expressed than by saying that this Being breathes its love.
But, if this expression is admissible, as the Word of the supreme Being is its Son, so its love may fittingly enough be called its breath (Spiritus). So that, though it is itself essentially spirit, as are Father and Son, they are not regarded as the spirits of anything, since neither is the Father born of any other nor the Son of the Father, as it were, by breathing; while p. 118 that love is regarded as the Breath or Spirit of both since from both breathing in their transcendent way it mysteriously proceeds.
And this love, too, it seems, from the fact there is community of being between Father and Son, may, not unreasonably, take, as it were its own, some name which is common to Father and Son; if there is any exigency demanding that it should have a name proper to itself. And, indeed, if this love is actually designated by the name Spirit, as by its own name, since this name equally describes the Father and the Son: it will be useful to this effect also, that through this name it shall be signified that this love is identical with Father and Son, although it has its being from them.