structural:reformatting, information:extraction, structural:summarization
Economic and immanent Trinity

The term "immanent Trinity" focuses on who God is; the term "economic Trinity" focuses on what God does. According to the Catechism of the Catholic Church,

The Fathers of the Church distinguish between theology (theologia) and economy (oikonomia). "Theology" refers to the mystery of God's inmost life within the Blessed Trinity and "economy" to all the works by which God reveals himself and communicates his life. Through the oikonomia the theologia is revealed to us; but conversely, the theologia illuminates the whole oikonomia. God's works reveal who he is in himself; the mystery of his inmost being enlightens our understanding of all his works. So it is, analogously, among human persons. A person discloses himself in his actions, and the better we know a person, the better we understand his actions.

The whole divine economy is the common work of the three divine persons. For as the Trinity has only one and the same natures so too does it have only one and the same operation: "The Father, the Son and the Holy Spirit are not three principles of creation but one principle." However, each divine person performs the common work according to his unique personal property. Thus the Church confesses, following the New Testament, "one God and Father from whom all things are, and one Lord Jesus Christ, through whom all things are, and one Holy Spirit in whom all things are". It is above all the divine missions of the Son's Incarnation and the gift of the Holy Spirit that show forth the properties of the divine persons.

The ancient Nicene theologians argued that everything the Trinity does is done by Father, Son, and Spirit working in unity with one will. The three persons of the Trinity always work inseparably, for their work is always the work of the one God. The Son's will cannot be different from the Father's because it is the Father's. They have but one will as they have but one being. Otherwise they would not be one God. On this point St. Basil said:

When then He says, "I have not spoken of myself", and again, "As the Father said unto me, so I speak", and "The word which ye hear is not mine, but which sent me", and in another place, "As the Father gave me commandment, even so I do", it is not because He lacks deliberate purpose or power of initiation, nor yet because He has to wait for the preconcerted key-note, that he employs language of this kind. His object is to make it plain that His own will is connected in indissoluble union with the Father. Do not then let us understand by what is called a "commandment" a peremptory mandate delivered by organs of speech, and giving orders to the Son, as to a subordinate, concerning what He ought to do. Let us rather, in a sense befitting the Godhead, perceive a transmission of will, like the reflexion of an object in a mirror, passing without note of time from Father to Son.

According to Thomas Aquinas the Son prayed to the Father, became a minor to the angels, became incarnate, obeyed the Father as to his human nature; as to his divine nature the Son remained God: "Thus, then, the fact that the Father glorifies, raises up, and exalts the Son does not show that the Son is less than the Father, except in His human nature. For, in the divine nature by which He is equal to the Father, the power of the Father and the Son is the same and their operation is the same." Aquinas stated that the mystery of the Son cannot be explicitly believed to be true without faith in the Trinity (ST IIa IIae, 2.7 resp. and 8 resp.).

Athanasius of Alexandria explained that the Son is eternally one in being with the Father, temporally and voluntarily subordinate in his incarnate ministry. Such human traits, he argued, were not to be read back into the eternal Trinity. Likewise, the Cappadocian Fathers also insisted there was no economic inequality present within the Trinity. As Basil wrote: "We perceive the operation of the Father, Son, and Holy Spirit to be one and the same, in no respect showing differences or variation; from this identity of operation we necessarily infer the unity of nature."

The traditional theory of "appropriation" consists in attributing certain names, qualities, or operations to one of the Persons of the Trinity, not, however, to the exclusion of the others, but in preference to the others. This theory was established by the Latin Fathers of the fourth and fifth centuries, especially by Hilary of Poitiers, Augustine, and Leo the Great. In the Middle Ages, the theory was systematically taught by the Schoolmen such as Bonaventure.