Denial of the Doctrine of Divine Simplicity is Platonic

Without a strong account of divine simplicity, the ultimate principle and explanation for the being and perfections of things in the world, yea even for God himself, must be sought outside of and back of God. This is, in effect, to offer a Platonic vision of the world in which even God possesses being and attributes through participation in ideal forms or universals.


God's Image as Analogy

Though creatures bear the image of God’s existence and attributes, their similarity to God is better understood as analogical than univocal. The manner in which God exists and possesses attributes is so radically unlike anything found in creatures that he cannot be classified together with them in a single order of being or as the highest link on a great chain of being. As the one who ultimately accounts for being in general, as its first and final cause, God does not stand within that general ontological order.


Union with Christ: Justification Does Not Cause Sanctification

Union with Christ is the ground of both justification and sanctification, and Christ is the meritorious cause of both. Just as sanctification does not cause justification, so justification does not cause sanctification, understood in terms of the order of salvation. Sanctification would be utterly impossible, apart from having been justified. But that does not mean that justification, as an applied benefit, can cause another applied benefit. Rather, the peace that we have with God because of our justification enables us to live out the sanctified life as a child of God.


God is Without Parts

This simplicity is of great importance, nevertheless, for our understanding of God. It is not only taught in Scripture (where God is called “light,” “life,” and “love”) but also automatically follows from the idea of God and is necessarily implied in the other attributes. Simplicity here is the antonym of “compounded.” If God is composed of parts, like a body, or composed of genus (class) and differentiae (attributes of differing species belonging to the same genus), substance and accidents, matter and form, potentiality and actuality, essence and existence, then his perfection, oneness, independence, and immutability cannot be maintained. On that basis he is not the highest love, for then there is in him a subject who loves—which is one thing—as well as a love by which he loves—which is another. The same dualism would apply to all the other attributes. In that case God is not the One “than whom nothing better can be thought.” Instead, God is uniquely his own, having nothing above him. Accordingly, he is completely identical with the attributes of wisdom, grace, and love, and so on. He is absolutely perfect, the One “than whom nothing higher can be thought.”


God's Essence is Absolutely Simple

Now, if God were of any causes, internal or external, any principles antecedent or superior to him, he could not be so absolutely first and independent. Were he composed of parts, accidents, manner of being, he could not be first; for all these are before that which is of them, and therefore his essence is absolutely simple.


John Owen, Vindiciae Evangelicae, "Mr Biddle’s Preface Briefly Examined", 72

God’s Essence is His Existence

...if the existence of a thing differs from its essence, this existence must be caused either by some exterior agent or by its essential principles. Now it is impossible for a thing’s existence to be caused by its essential constituent principles, for nothing can be the sufficient cause of its own existence, if its existence is caused. Therefore that thing, whose existence differs from its essence, must have its existence caused by another. But this cannot be true of God; because we call God the first efficient cause. Therefore it is impossible that in God His existence should differ from His essence.

Si igitur ipsum esse rei sit aliud ab ejus essentia, necesse est, quod esse illius rei vel sit causatum ab aliquo exteriori, vel a principiis essentialibus ejusdem rei. Impossibile est autem, quod esse sit causatum tantum ex principiis essentialibus rei, quia nulla res sufficit, quod sit sibi causa essendi, si habeat esse causatum. Oportet ergo, quod illud, cujus esse est aliud ab essentia sua, habeat esse causatum ab alio; hoc autem non potest dici de Deo, quia Deum dicimus esse primam causam efficientem; impossibile est ergo, quod in Deo sit aliud esse, et aliud ejus essentia.


Thomas Aquinas, Summa Theologia, 1.3.4

What is the Doctrine of Divine Simplicity

Adherents to this doctrine reason that if God were composed of parts in any sense he would be dependent upon those parts for his very being and thus the parts would be ontologically prior to him.


Simplicity is the ontologically sufficient condition for God’s absoluteness. The doctrine of divine simplicity teaches that (1) God is identical with his existence and his essence and (2) that each of his attributes is ontologically identical with his existence and with every other one of his attributes.


God’s Essence is His Existence

Thomas’s greatest contribution to the advancement of the DDS is found in his teaching that every created thing, even relatively simple things such as human souls and angelic spirits, are at the very least composed of existence and essence. No created essence is identical with its act of existence and is therefore relative and dependent in some sense. But God’s essence is identical with his existence and therefore God is absolutely necessary and self-sufficient.


The Glory of the Beatific Vision

The glory of the beatific vision is bestowed according to an image paradigm, and an image presupposes a relationship between that image and the original. This relationship between God and the recipients of saving grace should be understood covenantally, that is, as a bilateral and reciprocal bond of fellowship between God and his people. Rather than conceiving of this communion as an ontological gift of self, it should be seen as an eschatological perfection of human nature. It is eschatological, not essentially ethical.