The mystery of the Trinity perplexes us and is beyond our understanding. If one omits part of the doctrine, one eliminates the perplexity but also misses the revealed reality; if one holds all of the doctrine but mistakenly thinks one understands it, one turns the perplexity into absurdity and also misses the only clue we have to the revealed reality. Thus it is important both to keep the doctrine intact and to realize the limits of one’s understanding of it.
One might omit part of the doctrine by supposing that the Father really is the one God, and that the Son and the Spirit are divine beings of a lower type. Or one might hold the equality of all three persons, but suppose each to be a particular something, just as three human individuals are equal as human persons, but each is a distinct particular. The former mistake would eliminate the threeness of persons; the latter would eliminate the unity in being, and substitute three “gods” for the one only God.
The propositions which the Church articulates in her teaching are closely based upon, although they develop, propositions expressed in Scripture. If one assumes that the expressions in these statements mean precisely what they would mean outside the context of revelation, then the mystery is reduced to absurdity: How can three distinct entities be identical with something one? This reduction to absurdity is avoided if one bears in mind that what is said of God always is said relationally. We do not know what God is in himself, but we do know that he reveals himself to us as the one only God, the God of Abraham and our God, and also as the Incarnate Son who relates personally with his heavenly Father, with whom he sends a Holy Spirit who is God with us (see Jn 14.16; 16.7).
“Person” said of Father, Son, and Spirit certainly does not mean what “person” said of human individuals means. This situation is not new; it did not arise because of modern developments in the understanding of human persons; it has been true since the doctrine first was articulated and will be so always. Yet as long as we call parents and children “persons,” we can hardly avoid saying that the one revealing himself as Father and Son is one God in distinct “persons.” Since they must be called “persons,” their Spirit also must be, lest his divinity be denied.22
22. Karl Rahner, S.J., The Trinity, trans. Joseph Donceel (London: Burns and Oates, 1970), 103–20, questions the suitability of the concept of “person” in the doctrine of the Trinity. In this questioning, he stresses the otherness of God, but he seems to fail to bear in mind this otherness when he deals with God’s unity. Rahner claims the concept of person is not used of God in the New Testament and the early Fathers. I think this claim is mistaken, since the lack of the word “person” is not the same as the lack of the concept of person. The concept is used in all New Testament talk about Father and Son. For a fuller development of this line of criticism, see Jean Galot, Le Christ, Foi, et Contestation (Chambray: C.L.D., 1981), 142–64.