Economic Versus Immanent Trinity
While the New Testament provides several references to the presence of the three persons of the Trinity and even more evidence about the specific work of the Father, Son, and Holy Spirit, the theology of the Trinity has an evolutionary history that required significant time before becoming the dogma that Roman Catholics profess today. This doctrine developed in ways that were chronologically consistent but theologically different in the Eastern and Western churches.
Later, St. Thomas Aquinas used the Augustinian idea of self-knowledge to create a similar Trinitarian analogy. He spoke of the unitary person as knower, known, and knowledge, as God is Father, Son, and Holy Spirit. Using natural reason, he used this analogy as a virtual proof of the Trinity.
Greeks in the Eastern Church concentrated on the Economic Trinity, the concept of how Father, Son, and Holy Spirit are experienced in the history of salvation. The Father is seen as the source and origin of all; he is the one to whom especially the name God belongs. The Son proceeds from the Father in an eternal generation (eternally begotten). Thus, the Son, too, is rightly called God. The Spirit proceeds from the Father through the Son. From the Greek perspective God has a nature that is dependent on the individual as any three humans have different natures and personalities that are dependent on the individual. The Eastern Church saw the Son as the image of the Father and the Spirit as the image of the Son. For the Greeks, God comes to humanity through the actions of the Son and Spirit. The Father is revealed through the Son; through the Son he reaches out to humanity in the actions of the Holy Spirit. Thus, God's contact with humanity is historically definite, through the actions of the Son, and immediate, through the actions of the Spirit.
The Latin Church developed the concept of the Immanent Trinity, meaning how the Father, Son, and Holy Spirit exist within the inner life of God. St. Augustine was a famous proponent of the Latin view. Starting with the concept of one divine nature, rather than three persons, he argued that the life of God was by its very nature necessarily Trinitarian. For him the divine nature precedes any concept of individual personalities as articulated in the East. Similarly, Augustine claimed that every action of God was an action of the Trinity; no individual action can be attributed to any one of the persons.
In order to explain his idea he used the mind as an analogy and metaphor. He said the mind was composed of memory, cognition, and thinking. All three of these ideas are endemic and vitally important to the brain as a whole. Augustine argued that the three members of the Trinity were also of equal importance and, therefore, shared equally divine being.