All the major Christian traditions maintain the doctrine of the Trinity: that God is defined as three persons: the Father, the Son (Jesus), and the Holy Spirit. The three persons are distinct, and yet one in “substance, essence or nature.” They are co-equal, co-eternal, and co-substantial. Each is God, wholly and completely. Despite this, however, the Son was “begotten” of the Father and the Holy Spirit “proceeds” from both.
The Bible contains no express formulation of the Trinity. Instead, it was developed by Christian theologians over several hundred years attempting to explain the perplexing relationship described by the Bible among God, Jesus, and the Holy Spirit. Many biblical passages described God as the only divine being, while others suggested that Jesus was also divine. Some passages appeared to describe Jesus as fully human while others appeared to describe him as a spirit. Some passages suggested the Jesus was created by God while others indicated that Jesus was eternal.
According to theologian Alister McGrath, the doctrine of the Trinity was necessary to harmonize these apparently contradictory passages. The God described throughout the New Testament writings could only be understood in “Trinitarian terms.” In other words, faced with a mishmash of apparently inconsistent biblical claims about God, Jesus, and the Holy Spirit, theologians had to invent a doctrine that appeared to make sense of it all. Thus was born the Trinity.
The Trinity didn’t gel until the fourth century, before which various other solutions were proposed, such as Binitarianism (one deity in two persons, or two deities), Unitarianism (one deity in one person), and Modalism (one deity manifested in three separate aspects). The church leaders of the day, however, ultimately rejected all these, awarding Trinitarianism the brass key as the best of the lot.
From the beginning, it was clear that this was a pretty fuzzy concept. St. Augustine was one of the earliest proponents of the doctrine. But even he acknowledged that it could not be coherently explained. According to Augustine, an explanation was beyond human comprehension, so one simply had to accept it on faith.
Since the fourth century, nothing has changed. The Oxford Dictionary of the Christian Faith defines the Trinity as “a mystery of faith revealed in scripture, historically being deemed unknowable by unaided human reason and not capable of logical demonstration once revealed, being above reason without being incompatible with the principles of rational thought.” In other words, no one has made sense of it to date, and there is no reason to expect that anyone ever will.
This is not to say that many modern apologists haven’t taken a crack at a coherent explanation. You can read many of them online. But I’ll save you some time. They’re all over the place. To say they’ve failed to reach a consensus is a vast understatement. You would be hard pressed to find any significant agreement among them.
And I will ask, if God existed, would he be okay with the fact that all of humanity is hopelessly confused over his very nature – especially when this confusion stands as a roadblock to many accepting his existence? Why would anyone worship a God they have no hope of understanding? And yet God provides no guidance – no intelligible explanation.
To accept the Trinity, we must adopt a position that makes no sense to us. But what justifies us in adopting an incoherent position when a perfectly coherent and plausible one is available? Isn’t it more likely that the entire notion of the Trinity is a hopelessly convoluted, but completely human, attempt to make sense of disparate and unrelated ideas – ideas that were never intended to be read together in the first place?