Absolute Divine Simplicity (ADS) and the Trinity

Absolute Divine Simplicity: Distinctions (plurality) is a Given

Aquinas returns to Divine simplicity in his answer: simplicity implies immediately that the essence of God can be identified with each Person. However, this answer is troubling in that we’ve spent many questions demonstrating the distinction between the Persons and now we seem to be saying that really they are the same. Some theologians, recognising this difficulty, proposed that we can find some way to distinguish between Person and essence. Aquinas rejects this saying that the relations in God (which define the Persons) are the Divine essence because of Divine simplicity. We must affirm that essence and Person are the same reality whilst simultaneously holding that there is a real distinction among the Persons. To reconcile this apparent paradox we remember that a Person is a relation subsisting in the Divine nature; the distinction between the Divine essence and the Persons is not a real distinction but a conceptual one (Question 39 - The Persons in Comparison to the Essence, READING THE SUMMA, 2011).

The divine hypostases does not infringe upon Divine simplicity because they themselves were grouped together with their own attributes (their common substance or nature: secondary ousia). Hence, the one God is the single substance and inside this single substance is the Father, Son and Holy Spirit, and all of what is common to them (omnipotence, omnipresence, omniscience, holiness, eternality, etc.). The divine attributes are plural and truly distinct but they are in reality forming strictly one reality (i.e. the single divine substance: the one God). To be more clear, i will explain more:

Likewise, the Trinity is the one God due to their relation to the single divine substance because they are in it, together with the attributes. The single divine substance is not only comprised of attributes but also of hypostases. The Father, Son and Holy Spirit, + omnipotence, omniscience, omnipresence, etc. are all together forming the single divine substance. The three divine hypostases are not only possessing the one substance, but that they also are the one substance themselves (Trinity is the one divine substance = one God).

(source: Summa Theologica: First Part By St. Thomas Aquinas, Page 185)

If the divine attributes, plural ( omnipotence, eternality, holiness etc.) and singular (as substance) at the same time (simultaneously) is compatible with absolute divine simplicity, the three divine hypostases themselves, being the plurality inside the one divine substance (i.e. God) is compatible with absolute divine simplicity. In absolute divine simplicity, distinctions (plurality) naturally exists because there is no single substance without a further description of that substance, in the same exact way that no single word is without definition/meaning (comprised of many words/letters).

Secondary Ousia of the Trinity: Species, not Genus

The divine essence is one and indivisible. It is under the category of secondary ousia (specifically in the sub-type: species, not genus). By being of single species, absolute divine simplicity is logically possible. If the three divine hypostases possess the same genus, they themselves would be three species ( = three Gods). This cannot be because their substance is one and cannot be divided, it can only be individuated. For instance, the man, dog and bird are three species under the same genus: animals. Thus, the three hypostases themselves, are of one species: only one God.

You are correct. Absolute Divine Simplicity is incompatible with Christian dogma because it is a pagan doctrine imported from Plato and Aristotle. Thomism is essentially modalism (Sabellianism). It teaches that the divine persons are relations within the divine essence. The Father is the divine essence qua begetting; the Son is the divine essence qua begotten; and the Holy Spirit is the divine essence qua proceeding (Alexander of Hales taught the same thing, and both based themselves on Peter Lombard's Sententiae, which was approved as dogma in Canon 2 of the Fourth Lateran Council in 1213-1215). This doctrine was ultimately borrowed from Boethius' De Trinitate. Saint Augustine explicitly rejects such a doctrine in Book 7, Chapter 6 of the Trinity:

For if to be is said in respect to Himself, but person relatively; in this way we should say three persons, the Father, Son, and Holy Spirit; just as we speak of three friends, or three relations, or three neighbors, in that they are so mutually, not that each one of them is so in respect to himself. Wherefore any one of these is the friend of the other two, or the relation, or the neighbor, because these names have a relative signification. What then? Are we to call the Father the person of the Son and of the Holy Spirit, or the Son the person of the Father and of the Holy Spirit, or the Holy Spirit the person of the Father and of the Son? But neither is the word person commonly so used in any case; nor in this Trinity, when we speak of the person of the Father, do we mean anything else than the substance of the Father. Wherefore, as the substance of the Father is the Father Himself, not as He is the Father, but as He is, so also the person of the Father is not anything else than the Father Himself; for He is called a person in respect to Himself, not in respect to the Son, or the Holy Spirit: just as He is called in respect to Himself both God and great, and good, and just, and anything else of the kind; and just as to Him to be is the same as to be God, or as to be great, or as to be good, so it is the same thing to Him to be, as to be a person.

Saint Augustine believed that the names of Father, Son, and Holy Spirit are relational, not the actual persons. The only problem with Saint Augustine's scheme is that it was imprecise. Not everything in God can be classified either as "ad se" or as "ad invicem". The essence, persons, and attributes of God are all "ad se", but they are not identical.

Orthodox Christianity (as expressed most clearly in the writings of Saint Gregory Palamas) preserves the distinction between Essence and Persons and between Essence and Attributes. For more information:

• Roman Catholic Absolute Divine Simplicity Refuted

• St. Gregory Palamas and the Tradition of the Fathers

P.S. Aquinas also believed that creation is patterned on ideas in the essence of God. If this is true, it means the world is divine and was not created by free will ex nihilo. i.e. Thomism teaches pantheism.