On the Reasons of the Holy Spirit, Book II

And so, limbs, operations, affections, and changes are written of God, even though He is infinite and immutable, because we could not otherwise express the power of the Creator. The impiety of the Manichæans a dualist sect, asserting two gods, is also exploded rather than just heresy. For since God is most perfect, and consequently most powerful, He would be neither if He had a companion, even a good one. For that which has a companion is not excellent. We cannot understand that which is most powerful to be that which, existing as good, admits the partnership of evil naturally repugnant to itself, or conversely, that which is evil, being what it is, suffers what is contrary to itself. For in lowest things, a command will be impatient of a partner, how much more so in the most perfect cause? Also exploded by the reason of perfection is the impiety of Muhammad and his followers, and likewise the atheist godless impiety of Lucian, which denies that there is a Trinity in God. For it is necessary that whoever acts, makes, or creates anything must be powerful enough to do that thing, and likewise must be so skilled in its composition that not even the smallest part of what is to be done is unknown, before the will proceeds into knowledge, nothing happens. For unless He wills, knows, and is able, He does nothing: these are the most perfect properties of God, which are called Persons and the Holy Trinity, the trace of which I showed to be everywhere in the first book On the Concord of the World original: "de orbis concordia", and in the first of the Sacred Proofs original: "sacrarum apodixeon". Therefore, the theopneustos God-breathed holy scripture, with names accommodated to our fragility, calls the power remaining unmoved in itself the Father, the wisdom proceeding from the power from eternity by way of generation the Son and Word, the will or love, or affection toward the things themselves, the Holy Spirit.