by Matt Slick
How does the doctrine of Divine Simplicity relate to the doctrine of the Trinity? In order to answer the question we must first define our terms.
In the doctrine of the Trinity, we have the teaching that there are three, eternal, distinct persons: the Father, the Son, and the Holy Spirit. Each of the three persons possesses the nature of divinity yet there are not three gods but one. This is a well-known doctrine within Christianity. However, the doctrine of God's divine simplicity is not nearly as commonly understood.
"Divine simplicity is the teaching that God is without parts but is instead a single metaphysical essence. He is simple, not compound; hence, divine simplicity. He is not made up of various compartments like goodness, love, and justice that combine to form a whole. Nor are the three persons in the Trinity, three parts that make up the totality of God. Instead, he is goodness, love, justice, etc. To reiterate, there are no components, no sections in his essence. There is no sense in which one aspect of his being (i.e., love) is above or more significant than any other (i.e., justice). God is equally perfect in all his qualities. Therefore, God is equally loving and just, equally compassionate and wrathful, equally rational and good, etc. There are a perfect balance and harmony of all of God's characteristics. Therefore, we would say God is equally loving, just, holy, patient, kind, omniscient, omnipresent, etc. We would not say that each of these is a part of what God is. Instead, they are all that God is. This further means that there is no distinction between his essence and his existence since he has the characteristics of eternality and omnipresence. Both are necessarily part of God's being. " /what-is-divine-simplicity-and-is-it-biblical
At this point, we must admit that there are difficulties in comprehending how the nature of God's simple essence can also be revealed in Trinitarian form. Doesn't the Trinity mean that God is not "simple" and that he is actually compound since he is comprised of three persons? No, it does not. Let me explain.
We see in the doctrine of the Trinity that God exists as three simultaneous persons. Each of the persons is divine in essence. We would not say that the Father is one-third of the Trinity, that the Son is also one-third, and the Holy Spirit is another third. There are not three "thirds" that make a whole. That would be "parts" and God is not three parts. Instead, the Trinity helps us understand the relationship that each of the persons has in the Godhead to the others. The Father is not begotten, but the Son is. The Holy Spirit is sent by the Father and the Son, but the Holy Spirit does not send the Father or the Son (see Economic Trinity). God is one in essence and his essence is not comprised of sections, parts, or components. Therefore we would say that the Trinity is an attribute of God's essence.
The Trinity reflects the divine simplicity of God when we see the three persons as the single Being who cannot be broken down into constituent parts; otherwise, each person is a third of God. Just as the one God has attributes of goodness, kindness, mercy, love, etc., the attribute of God's nature is that he is Trinitarian. And, we experience the Trinity through the revelation of Scripture, as three divine, simultaneous, coeternal persons. But, this does not mean that God is composed of three parts: Father, Son, and Holy Spirit. Instead, whatever each person of the Trinity is, so also is the whole of the Trinity. Each is identical in regards to the divine nature.