The objection
If love requires a counterpart, two persons suffice. If attributes establish persons, wisdom, power or righteousness could also be distinct persons. Why should there be exactly three?
1. We do not calculate God's inner life
Scripture reveals the Father, the Son and the Holy Spirit. It reports their relationships and shared divine activity. The number three rests on this. The confession does not arise by first assuming an indefinite God and then considering how many persons would be useful for his attributes.
Thomas rejects precisely this confusion: Creaturely effects cannot simply be turned into proof of particular persons within God. We owe our knowledge of these persons to revelation.[1]
2. Attributes are no additional agents
God is wise, righteous and powerful. It does not follow that “wisdom,” “righteousness” and “power” are three further persons. Such concepts say how God is. Personal statements, by contrast, name who stands in relationship to whom: The Father loves the Son; the Son asks the Father; the Spirit is sent as another Advocate.
Even when Christ is called God's wisdom, the Father is not thereby without wisdom. An attribute particularly assigned to a divine name is not cut out of shared divine being and made independent.
3. The Spirit is not merely a third word for the same relationship
John 14,16 distinguishes the asking Son, giving Father and other Advocate. John 15,26 adds the Spirit proceeding from the Father whom the Son sends and who bears witness to him. The Spirit is thus not simply the Father under another name, nor the Son in a later role.
The Trinitarian reading therefore needs no speculative leap from two persons to a third. It follows a distinction already described in the text.
4. What the argument from love can achieve
John 17,24 attests the Father's love for the Son before the world. God did not have to create creatures to love for the first time. This illuminates his love's independence from us. But it proves by itself neither the number three nor the precise manner of the Spirit's procession.
Adding a fourth person would be no necessary deepening of this evidence but an unjustified addition. We confess the fullness revealed by God. We do not claim to have produced it through a calculation independent of his revelation.
Biblical texts in context
Sources and further study
- Thomas Aquinas, Summa theologiaeI, q. 32, a. 1: no natural demonstration of the number three; distinction between revelation and explanation.