Q. What is the meaning and significance of our confession of the “homoousia” and “perichoresis” of Father Son and Spirit? How does this speak to the unity or simplicity of God?
A. By this we confess that each member of the Trinity, while distinct in subsistence (or self-awareness), is of the same substance (meaning that they are each fully, truly and eternally God) and that each mutually indwells the others so as to eternally coexist as one, unified God (Jn. 10:38, Rom. 8:9-11). By this we affirm that God is one God (Deut. 6:4), and that he is indeed three persons who mutually glorify one another and participate in all of his works (albeit with different emphases and focuses), thereby drawing believers to participate in the life of the Trinity. (Originally published in a Catechism I turned in to Dr. Clark at the Moody Bible Institute for Systematic Theology I)
Perichoresis is not a word you’d commonly hear in conversation. It is, however, an important theological term with huge implications on Christian faith and worship, and when you finish reading this post, I hope you’ll understand why.
The dictionary definition of perichoresis is hard to track down, as it does not appear in many dictionaries, but essentially, this word refers to a mutual indwelling which the members of the Godhead experience. That is, as they enjoy fellowship within the Trinity (more on that later) they each uniquely interact with each other, always in perfect harmony and with one purpose of mind. In all, they glorify each other and are equally involved in all his works. This understanding of the Trinity has been part of orthodoxy for nearly 2,000 years, with few changes or adjustments.
How does it apply to Christian life though? First, it gives us an example for how to live in fellowship with God. Since he has existed for all of eternity in perfect fellowship among his Trinity, he is the perfect example for our relationships with each other and with him. Additionally, with a correct understanding of the Trinity, specifically of the relationship between the members of the Trinity, we can begin to understand the reality of our existence as the overflow of God’s perfect love which has always existed in that context. For more on this, read Michael Reeves’ book Delighting in the Trinity.
When thinking about this, it is helpful to consider God as Trinity in terms of oneness. That is, in affirming the distinctiveness of each of the three persons of the Godhead, we must carefully affirm him as the one true God (Deuteronomy 6:4). There is no division within him, and there can be no discord between the members of the Trinity.