Over on Catechumen’s Walk there’s been a discussion of the nature of the Holy Trinity (Inner-Trinitarian Relationships, 9/22/04). Here follows St Basil the Great, whose treatise “On the Holy Spirit” is a classic exposition of trinitarian doctrine:
When the Lord taught us the doctrine of the Father, Son, and Holy Spirit, He did not make arithmetic a part of this gift! He did not say, “In the first, the second, and the third,” or “In one, two, and three.” He blessed us with the knowledge given us by faith, by means of holy Names. We are saved through faith; numbers have been invented as symbols of quantity. These men bring ruin on themselves through every possible source; they have even turned man’s ability to count against the faith! Numbers cannot change the nature of anything, yet these men honor arithmetic more than the divine nature, lest they give the Paraclete more honor than He is due! But the Unapproachable One is beyond numbers, wisest sirs; imitate the reverence shown by the Hebrews of old to the unutterable name of God. Count if you must, but do not malign the truth. Either honor Him Who cannot be described with your silence, or number holy things in accord with true religion. There is one God and Father, one Only-Begotten Son, and one Holy Spirit. We declare each Person to be unique, and if we must use numbers, we will not let stupid arithmetic lead us astray to the idea of many gods.
If we count, we do not add, increasing from one to many. We do not say, “one, two, three,” or “first, second, and third.” God says, “I am the first and I am the last.” We have never to the present day heard of a second God. We worship God from God, confessing the uniqueness of the persons, while maintaining the unity of the Monarchy. We do not divide divine knowledge and scatter the pieces to the winds; we behold one Form (so to speak) united by the invariableness of the Godhead, present in God the Father and God the Only-Begotten. The Son is in the Father and the Father in the Son; what the Father is, the Son is likewise and vice-versa — such is the unity. As unique Persons, they are one and one; as sharing a common nature, both are one. How does one and one not equal two Gods? Because we speak of the emperor, and the emperor’s image — but not two emperors. The power is not divided, nor the glory separated. One is the dominion and authority over us; we do not send up glories to God, but glory; the honor given the image passes to the prototype. The image of the emperor is an image by imitation, but the Son is a natural image; in works of art the likeness is dependent on its original form, and since the divine nature is not composed of parts, the union of the persons is accomplished by partaking of the whole. The Holy Spirit is one, and we speak of Him as unique, since through the one Son He is joined to the Father. He completes the all-praised and blessed Trinity. He is not ranked with the plurality of creation, but is described in the singular; this is sufficient evidence of His intimacy with the Father and the Son. He is not one of many but one only: just as there is one Father and one Son, there is one Holy Spirit. Reason demands that the singular is separated from the plural or compound; therefore He does not share created nature. He is united to the Father and the Son as unit dwells with unit.
There’s more where that came from. It’s a wonderful study in theological debate of the time — its lessons for all time.