How did the Church come to understand the mystery of the Holy Trinity?

Answer 1

Answer
The word 'Trinity' is not actually used in The Bible, but there are passages that some see as referring to the Trinity. One of the most famous of these is the "Johannine Comma" (1 John 5:7), which refers indirectly to the concept of the Trinity. This was never in the early Greek manuscripts, only appearing in the Latin translation of the fifth century, after the Trinity doctrine had been accepted by the Council of Nicaea.

It appears likely that the Gnostic leader, Valentinus, was the first to formulate the concept of the Holy Trinity. His work, On the Three Natures, is mentioned by Marcellus of Ancryra, who said that the now-lost work discussed the Father, Son and Holy Ghost as three Persons of the Trinity. Tertullian, who was also familiar with Gnostic thinking, was an early advocate of the Holy Trinity.

The early Church Father, Eusebius, implied, rather than saying explicitly, that the true Church had taught the same things from the time of the apostles to his own, yet his position on the Trinity was evolving over time. He wrote at a time when the concept of the Trinity was yet to be agreed.

Early in the fourth century, Arius, a popular Libyan priest, declared that Christ, while divine, was not divine in the same way as God the Father. Around 318, Alexander, bishop of Alexandria, declared heretical the views of Arius and had him, and the clergy who supported him, excommunicated. Alexander had the wording that Christ was "of one being with God" adopted at the Council of Nicaea in 325. It took some decades for the Catholic-Orthodox Church to establish an agreed concept of the Holy Trinity. The Arians, followers of Arius, rejected this view.

The Nicene Creed states that the Holy Spirit "proceeds from the Father." It does not say explicitly that the Holy Spirit proceeds from the Son as well as the Father, and there is no statement that the Spirit's eternal origin is found anywhere but in the Father. The third Ecumenical Council, the Council of Ephesus in 431 forbade any further changes to the Creed, except by another such council. The phrase "and the Son" (Latin: filioque) was used in a letter from Pope Leo I to the members of the Synod of Toledo in Spain in 447. In the ninth century, Pope Leo III (795-816) agreed with the filioque theologically but was opposed to adopting it in Rome. In 1014, the German Emperor Henry II of the Holy Roman Empire visited Rome for his coronation and found that the Creed was not used during the Mass. At his request, the Bishop of Rome added the Creed, with the filioque. This was the first time the phrase was used in the Mass at Rome. The Schism between the Western Church and the Eastern Churches was triggered by the insertion by Rome of the filioque clause into the Nicene Creed. The Eastern Churches have never accepted this definition.

The Concept of the Holy Trinity that is now accepted by most Western Churches came about by means of charismatic leadership, brinkmanship and political dealmaking.