Trinitarian Truth

Among the most controversial aspects of Christian theology, through most of its his history, is the Trinity doctrine. In the simplest possible terms, this is the assertion that:
The Father (YHWH of the Old Testament), the Son (Jesus Christ) and the Holy Spirit (Holy Ghost, or the Paraclete) comprise the Godhead, or God, in His entirety
Each of these divine Persons, individually, is at the same time also fully God in His/Its own right, nevertheless
Each of these divine Persons is also fully distinct, having functions or duties totally unique to Him/It
Yet, even though they function separately, and are independent beings, they are nevertheless united in purpose and action, and united as one God
The problem with the Trinity doctrine, then, is that on its face, it makes little sense. While it has long been accepted as a “mystery,” an aspect of God which is beyond human understanding, this was not always the case. If it had been, then it would not have been so controversial. In fact, had it been developed on its own, no controversy would have erupted at all.
The underlying basis for what eventually became the Trinity concept did exist as a tentative or nebulous idea in the heads of some early Christian writers, but was never laid out specifically until the middle of the 4th century. This was the practical start of the Trinity doctrine. I will, however, begin with the theoretical origins of the Trinity, then move on to its practical origins (i.e. when it became a part of Christianity’s central theology).

The Trinity in Early Theory

“Trinity” is the modern English translation of the Greek τριας (trias), of which trinitas was the usual Latin translation. It might also be translated into English as “triad.” As part of its defense of this doctrine, the Catholic Encyclopedia points out that in the late 2nd century, Theophilus of Antioch mentioned a trias of θεος (theos, “God”), λογος (logos, “Word”), and σοφια (sofia, “Wisdom”).
Really, though, even this is not novel; the gospels speak of the Father, Christ, and Paraclete, and these were commonly interpreted as God, Word, and Wisdom. In fact, more mystical versions of Christianity, especially some Gnostic sects, had cosmologies in which there was an Ineffable Divine, from whom Christ and Wisdom both emanated (along with many other emanations, too).

Other Church Fathers refer to the “divine triad,” if you will. Among the most important of these was Tertullian, who — because he wrote in Latin — provided the origin of the English word “trinity” (i.e. his Latin trinitas). Given the scriptures they had before them, the Church Fathers hardly could have failed to do so. Even so, they didn’t develop this into a doctrinal or theological point; it appears they saw no need for any such thing, that the mentions of the three divine Persons in scripture were self-sufficient.

Practical Origins of the Trinity

The Trinity doctrine did not come into existence as its own piece of theology. Rather, it evolved over time as the orthodox (or Alexandrine) Christian response tothe Samosatene/Arian doctrine. In order to condemn Arius and the Gnostics as well, the Council of Nicaea determined that Christ and God were separate yet unified, each fully God. This was merely a statement of belief, not by itself a theological concept.
What Nicaea left out, of course, was the Holy Spirit. The controversy leading up to that Council was, rather specifically, the nature of Christ and his relationship to God the Father. The Holy Spirit’s nature was not addressed; literally, then, Nicaea could not have produced a “Trinity”; at best, it produced only a “duality.”

Developing the theology needed to back up this belief, fell to a number of Church leaders, perhaps the most important being Athanasius of Alexandria (and, while he lived, Athanasius’ mentor, Patriarch Alexander). As a way of bolstering their theology, they took up the matter of the Holy Spirit’s divinity, as well. The essential foundation of this doctrine was threefold:

Christ was with God in the beginning and was God (Jn 1:1)
Christ and God the Father are unified (Jn 10:30)
New Christians are to be baptized in the name of Father, Son, and Holy Spirit (Mt 28:19)
The Holy Spirit was not well-understood in early Christianity, however, the “unforgiveable-sin” injunction against blasphemy of the Holy Spirit (Mt 12:31-32) lent great weight to the importance of the third Person of the Godhead. This was used to support the Holy Spirit’s divinity, in the face of those who believed otherwise (especially the Macedonians).
One complication that early Trinitarians faced, was that their doctrine was so irrational, alien, and illogical, that the very tool needed in order to explain it, e.g. language, was quite simply not up to the task of describing it. They were forced to coin new words, such as ‘ομοουσιος (homoousios), meaning “one substance.” This, of course, didn’t help much, since words like homoousios didn‘t mean very much to the reader/listener, unless s/he already had some inkling of what the Trinity was supposed to be. One could understand what the Threee Persons of the Godhead having “one substance” meant, only if one already had some idea that they were somehow joined or linked as one … in which case, being told they had “one substance” no longer was very informative.

The various points of evidence came from the apostolic gospels (mentioned above) only gave the Trinity greater apparent authority — at least, in the eyes of those who supported it. Opponents used other scriptures (e.g. “the Father is greater than I,” Jn 14:28) to attack it, and they considered their evidence just as authoritative.

A point which cannot be missed here is that, in the early 4th century when the Trinity was first thought out, it was not the intended goal. Instead, the goal was to support a christology (in Athanasius’ case, the orthodox or Alexandrine; in the Arians’ case, the Samosatene/Arian doctrine). Attempting to understand the nature of God was actually secondary to the real effort, which was to bash one’s theological opponents.

Athanasius had a turbulent career, wrestling not only with his own see of Alexandria (which, for several generations after Nicaea, remained home to many Arians, who fought with him and even expelled him a couple of times), but with Christian thinkers in other regions who either opposed him, or else supported his orthodoxy but wished to go about it differently. The idea of a mysterious, inexplicable divine Trinity wasn’t without its critics, in the 4th century.

Athanasius ultimately forced his doctrine on his diocese and evangelized for it elsewhere. At the First Council of Constantinople in 381, the matter was taken up. Even prior to the invocation of the Council, Athanasius intimidated many of the bishops present; their adoption of the Trinity as one of that council’s canons might well be attributed to that.

First Council of Constantinople (381)

Although Athanasius and many of his allies had been deposed at the time, I Constantinople turned out to be everything they could have hoped for. The creed of Nicaea, in which Father and Son were united in divinity yet individually fully divine, was extended to include the Holy Spirit.
This Council enacted a creed which is, more or less, what is now known as the Nicene Creed. Properly speaking, it’s not the “Nicene” creed at all, and rather should be called the Constantinopolitan Creed. But it was called the New Nicene creed at the time, as a way of affirming all that had been done at Nicaea.

Later Trinity

Although this goes a bit beyond early Christianity, so I won’t go into great detail, it’s worth noting that the Trinity was an idea with which Christian thinkers grappled for many centuries (and they’re still doing so, even now). It’s difficult to understand or reconcile what amounts to the expression 3=1=3. Medieval scholastics tried but failed, ultimately deciding that only faith could resolve it for any given believer.
This has, ultimately, ended up being the position of most of Christendom: That the Trinity is true, even though it’s incomprehensible; faith is the only tool one can use to accept it.

What Is the Trinity?

Now that I’ve described the history behind the Trinity doctrine, it’d be best to wrap this up by stating what the Trinity doctrine says. Keep in mind that this doctrine is stated in different words by different Christian denominations, and this may or may not appear to agree with your denomination’s doctrine. It’s merely a general outline of what the Trinity says.
The three Persons — Father, Son and Holy Spirit — together make up the Godhead, or simply, God.
Each of the three Persons is, individually and simultaneously, fully God.
The Trinity does not claim that God is a collective divine Being, with each of the three Persons being a subset thereof; rather, each is wholly God, in addition to being a component of God along with the other two Persons.
This doctrine has been a stumbling block for Christians (and others!) since its inception. Its irrationality and illogic have led to various other ways of attempting to comprehend the Godhead, which — while they might make slightly more sense (e.g. the various forms of Modalism that have popped up over the centuries) — fall outside the strict definition of the Trinity and therefore are called non-Trinitarian. Christian believers and sects that have held such views … which, really, are modifications of the Trinity rather than outright rejections of it … have been subject to derision and even persecution by more orthodox Christians.
That the Trinity doctrine was constructed not out of a desire to understand God, but rather as part of a a vendetta against heresies (i.e. first Arianism, then Macedonianism), is what makes it as nonsensical as it seems. It was not designed as a rational theology and was never intended to be one; it was designed specifically, and only, to refute other theologies and to exclude those who adhered to them