Must You Believe in the Doctrine of the Trinity to Be a Christian?
Perhaps the most surprising aspect of twentieth century Christian theology was the renaissance of the doctrine of the Trinity. Throughout the nineteenth century (and perhaps before) the doctrine had become dormant. Conservatives took it for granted, deists and liberals tended to deny it or at least put it on the shelf and ignore it. Conservatives thought everything that could be said about it had been said; all that remained was to repeat it perhaps in fresh and more culturally relevant ways (although even that was rare). Liberals thought it was too mysterious, too irrational, for the modern age of reason. Most of the great theologians of Christendom got caught up in other doctrinal issues such as “kenotic Christology;” few dedicated attention to the doctrine of the Trinity so that by the first decade of the twentieth century it was either taken for granted (in its ancient formulations) or put aside.
Karl Barth brought the doctrine of the Trinity roaring back in Church Dogmatics, making it a centerpiece, a linchpin of Christian doctrine if not of the kerygma itself. Then came a slew of treatises on the doctrine of the Trinity from virtually every corner of Christendom. Among theologians who breathed new life into the ancient dogma were Claude Welch, Leonard Hodgson, Robert Jenson, Wolfhart Pannenberg, Jürgen Moltman, Eberhard Jüngel, Leonardo Boff, Ted Peters and Karl Rahner. So much did the situation turn around that many Christian theologians began to think that belief in the doctrine of the Trinity was part of the gospel itself and necessary for being a Christian.
One twentieth century theologian who challenged this assumption was Emil Brunner who, in Dogmatics I: The Christian Doctrine of God, argued that the doctrine of the Trinity is a “defensive doctrine” and not part of the kerygma. He did not go so far as to say one could be a Christian without believing in it, but that was implied. According to Brunner, the doctrine of the Trinity is a theological construct and necessary one but not something found in the New Testament itself. In other words, given heresies that arose in the period between the New Testament and the councils of Nicea and Constantinople, the construction of the doctrine of the Trinity (that God is one substance and three persons) was inevitable and necessary—to protect the revelation of God as Father, Son and Holy Spirit and yet one God (monotheism).
Implicit in Brunner’s treatment of this matter is a distinction between Trinity and the doctrine of the Trinity. In other words, according to Brunner, that God is Father, Son and Holy Spirit is revealed truth. That Father, Son and Holy Spirit are una substantia, tres persona, one ousia and three hypostases, is theological reflection on revealed truth the only value of which is to protect what is revealed from distortion by heresies.
I agree with Brunner that the doctrine of the Trinity is not part of the gospel; it is not revealed truth. It is constructed out of revealed truth and constitutes necessary reflection on revealed truth in the light of heresies (subordinationism, adoptionism, modalism, tritheism, etc.). Once the doctrine of the Trinity was constructed and embraced by the church ecumenical (Orthodox, Catholic, Protestant) it could not and should not be set aside, ignored or rejected. But neither should it be confused with revelation itself or the gospel of Jesus Christ.
Another way of putting that is that the doctrine of the Trinity is not what should be preached or witnessed about. It is not part of what Barth called the “Sache” (central subject matter) of the Bible; it is a necessary deduction from it. (I don’t think Barth always kept to that insight, though.) The doctrine of the Trinity and reverent, warranted speculation about the Trinity should be kept in the pastor’s study and theological classrooms (including Sunday School, catechism classes, etc.). Sermons should be informed by it but it should not be the point of any sermon.
How one can grasp the gospel and not believe in the doctrine of the Trinity is difficult to understand, but it happens. Many Christians simply cannot “wrap their minds around” the doctrine of the Trinity and so put it on a shelf, so to speak, and leave it there—neither believing it nor denying it. A few deny it simply because they misunderstand it and it’s difficult to blame them. According to a famous statement often attributed to St. Augustine “If you deny the Trinity you lose your salvation but if you try to understand it you lose your mind.” That’s the difficulty many Christians find themselves in and they feel caught between having to believe a doctrinal formulation they can make no sense of and being threatened with losing their status as Christian (if not their salvation).
Please don’t get me wrong; I think belief in the Trinity, that God is Father, Son and Holy Spirit and yet one God, is essential to authentic Christianity. But someone who demurs from confessing the “one substance, three persons” for reasons other than denial of the deity of Christ and the Holy Spirit, are probably just confused, mystified, perplexed. I would not join a church that did not confess the doctrine of the Trinity in some form (at least implicitly if not explicitly), but I cannot deny the Christian status of someone who is genuinely confused and uncertain about it.
A few years ago I visited a church that claims not to believe in the doctrine of the Trinity. A soloist sang a song titled “O Lamb of God” the first line of which says “From your side you sent your Son.” I tried to ask my friend who is an elder of the church how they can sing that song and mean it and at the same time deny the doctrine of the Trinity. He looked at me bemused and said “We believe whatever the Bible says.” Then I was bemused. My life experiences and reading of Brunner have led me to think that the doctrine of the Trinity, although extremely important as a landmark, if not a pillar, of Christian doctrine, is not essential to being Christian. But I suspect that if I could get any real Christian who claims not to believe in the Trinity alone in a room, one-on-one, for an hour long conversation about the matter I could convert them to belief in it.
In sum, then, I am suggesting that the doctrine of the Trinity lies in a liminal position between or overlapping the borders of dogma and doctrine as I described these as two of three categories (the third being opinion) of Christian beliefs. “Dogma” is the category of essentials of the Christian faith, what is required to believe in order to be considered Christian. There I would place the deity and humanity of Jesus Christ (incarnation). “Doctrine” (in the sense of this taxonomy) is the category of important but not essential beliefs. There I would place, for example, universal atonement. “Opinion” is the third category in which I would place premillennialism. (I explained these in much more detail in Who Needs Theology: An Invitation to the Study of God (IVP) and The Mosaic of Christian Belief: Twenty Centuries of Unity and Diversity (IVP).