Union and Communion with the Triune God

Truth should be practical, and the doctrine of the Trinity, being utterly true, surely ought to show itself practical in some way. "Sound knowledge," said James Ussher (1581-1656), is "knowledge which sinketh from the brain into the heart, and from thence breaketh forth into action, setting head, heart, hand and all a-work." This is especially the case with theological truth, which is why Ussher, a Reformed theologian and archbishop in the Church of Ireland, went on to admonish, "So much only must thou reckon thyself to know in Christianity, as thou art able to make use of in practice." (1)

But just how are we to make use of the doctrine of the Trinity in practice? The doctrine itself states nothing about who we are, how we exist, or how we should behave. It is manifestly and magnificently a very different kind of doctrine; one about who God is, how God exists, and how God behaves. The Westminster Confession of Faith summarizes the Trinity as follows:

In the unity of the Godhead there be three Persons of one substance, power, and eternity: God the Father, God the Son, and God the Holy Ghost. The Father is of none, neither begotten nor proceeding; the Son is eternally begotten of the Father; the Holy Ghost eternally proceeding from the Father and the Son. (2)

To follow those sentences with the charge "so act accordingly!" would be absurdly anticlimactic. Even the Heidelberg Catechism’so intent on teaching the immediate pastoral implications of doctrine’does not follow its presentation of the Trinity with its standard application question, "What benefit do you receive from this?" Instead it asks simply, "Since there is only one God, why do you speak of three persons?" (3) (Answer: "Because God has so revealed himself in his Word.") If even the Heidelberg doesn't readily deliver the practical value of the Trinity, perhaps we are seeking it in vain. Modern thinkers pretty uniformly assumed this to be the case, following Immanuel Kant who announced that "the doctrine of the Trinity provides nothing, absolutely nothing of practical value, even if one claims to understand it." (4)

Yet Reformation theology provides at least two resources that help us see what is practical about the doctrine of the Trinity. The first is the connection between knowledge of God and knowledge of the self, and the second is the biblical dynamic of union and communion.

Practical Knowledge of God and Self

First, the connection between knowing God and knowing the self shows that we cannot have accurate knowledge of God without simultaneously knowing ourselves to be different from God: dependent on him, infinitely less than God, rebellious against him. Conversely, we cannot have accurate knowledge of ourselves without becoming aware of God's exaltedness over us. The knowledge of both comes bundled together. Calvin opens his Institutes with this theme: "Nearly all the wisdom we possess, that is to say, true and sound wisdom, consists of two parts: the knowledge of God and of ourselves." (5) For the next thirteen chapters of the Institutes, he develops the knowledge of the true God (in contrast to idols) as culminating in revealed knowledge of God as Father, Son, and Holy Spirit. Only with this concrete knowledge of the true God in mind can we begin to understand ourselves; otherwise we are in constant danger of projecting a false god and consequently misunderstanding ourselves in relation to this imagined deity.

Just how specific and thorough our knowledge of God the Trinity needs to be is indicated by how long and detailed that thirteenth chapter of the Institutes is: knowledge of the Father, Son, and Holy Spirit is the capstone of Calvin's treatise on knowing God.

But an even clearer example can be seen in a later popularization of the theme of knowledge of God and knowledge of self. One of the best-selling devotional books of all time is The Practice of Piety: Directing a Christian How to Walk That He May Please God by Lewis Bayly (d. 1631). An eminently practical book that gave believers counsel for various phases of life, Bayly's The Practice of Piety was widely influential. Two examples show its popularity: When John Bunyan married, his wife brought two books with her into the marriage, one of which was Bayly. And when missionary John Eliot finished translating the Bible into Algonquin for the Native Americans, his next project was to translate The Practice of Piety.

Bayly begins The Practice of Piety by saying, "Forasmuch as there can be no true piety without the knowledge of God; nor any good practice without the knowledge of a man's own self; we will therefore lay down the knowledge of God's majesty, and man's misery, as the first and chiefest grounds of the Practice of Piety." And the knowledge of God that he teaches is knowing "the diverse manner of being" of the three persons in the divine essence. Bayly takes his readers through a careful account of the three persons, always beginning with who each person is in the Trinitarian life itself: "The first Person is named the Father; first, in respect of his natural son…the second Person is named the Son, because he is begotten of his Father's substance, or nature." In short, Bayly judged that in order for a believer "to walk that he may please God," a great deal of Trinitarian theology was necessary and helpful. Imagine translating into Algonquin passages such as, "The divine essence is in the Father unbegotten, in the Son begotten, and in the Holy Ghost proceeding, we make not three essences, but only shew the diverse manners of subsisting"! In this tradition, Trinitarian theology does not dictate any specific ethical commands, nor does it prescribe any sort of program for imitating the Trinity's tri-unity; in my judgment this is all to the good. Instead, Bayly considers Trinitarian theology to be the only route to accurate knowledge of who God essentially is, and reckons that believers have no other path to accurate self-knowledge than to know who their God is.

Union and Communion

The second resource that Reformation theology brings to bear on showing how the doctrine of the Trinity is practical is the dynamic of union and communion. The believer's union with God in Christ is the foundational reality, the accomplished and perfect work that brings us into the saving relation with God. From that union arise specific acts of communion, or experiences of fellowship, with God. "Union is the foundation of communion," said Richard Sibbes. (6) It was the Puritan authors who made the most of this distinction. When they wrote actual theological treatises, they tended to focus on union with Christ and its foundational reality. But when they preached, or published their sermons in the form of spiritual or what we might call devotional writing, their focus shifted to acts of communion. The reason is obvious: Communion comes into the realm of actual experience; unlike union, it rises and falls; it can be increased or can suffer diminishment; it can be cultivated or neglected. While it would make no sense to tell a congregation to "get more united to Christ," it makes perfect sense to exhort them to engage in spiritual disciplines and stir themselves up to improve their communion with God.

We can observe the same dynamic when it comes to Christian experience of the Trinity. Foundationally, Christian existence is existence in union with the Trinity. Our union with Christ the incarnate Son reconciles us with his Father and fills us with his Spirit; to be saved is to be brought into saving contact with the God who is Father, Son, and Holy Spirit. There is a Trinitarian depth to Christian salvation that necessarily results from the Trinitarian nature of the God who saves. The gospel, even when it is expressed in a way that does not make the doctrine of the Trinity explicit, is always an engagement with the Trinitarian God. This is because the publication of the gospel is not a side project for God but an action that comes from his heart, which emerges from his inmost being. It is an undertaking to which Father, Son, and Holy Spirit commit themselves fully. As Thomas Goodwin wrote, "The things of the gospel are depths… the things of the gospel are the deep things of God." (7)

Built on this fundamental union is communion with the Triune God, which is something that varies from church to church, from time to time, and from one believer to another. John Owen (1616-1683) wrote the classic treatise on the subject of the believer's Trinitarian fellowship: Of Communion with God the Father, Son, and Holy Ghost. (8) There, Owen describes the sort of communion we have with God, a communion that "consisteth in his communication of himself unto us, with our returnal unto him of that which he requireth and accepteth, flowing from that union which in Jesus Christ we have with him." (9) Considering first the Father, then the Son, and finally the Holy Spirit, Owen attentively traces what the Bible teaches about each person's movements toward us in Christ, and our most appropriate "return­al" or responses to that particular person. Attending to these makes for a rich biblical theology, highlighting "the grace of our Lord Jesus Christ, the love of God [the Father], and the fellowship of the Holy Spirit" (2 Cor. 13:13). All of this communion flows from God in a Triune way, which Owen summarizes in the formula, "The Father does it by the way of original authority; the Son by the way of communicating from a purchased treasury; the Holy Spirit by the way of immediate efficacy." (10) We could say it more concisely: Our fellowship with God is from the Father, through the Son, in the Spirit.

The fact that our threefold communion is "bottomed upon" a union with the Trinity has far-reaching implications for our understanding of salvation, for our worship together, and for our personal prayer. Salvation makes most sense when it is understood in most Trinitarian terms; for instance, not bluntly as "getting saved" but more abundantly as being adopted by the Father through the only-begotten Son and receiving the Spirit of adoption. In our worship, we do not need to rehearse all the theological terminology of Trinitarian theology (valuable as it is in its proper place), but we do need to be reminded consistently through Scripture, hymn, and prayer that our worship is directed to this particular God, the true one. And in personal prayer, there is a great advantage to becoming increasingly aware that all Christian prayer is directed to the Father through the Son in the Holy Spirit, whether or not we are attending to its direction. Prayer has a current of mediation running through it, a Trinitarian directionality built into it as a result of our communion being grounded on our union.

When our liturgies and personal devotions feel weak, rote, and ineffective, we need to remember that these are only expressions of our communion with God, while beneath them are the everlasting arms of actual union with Christ. When our intellectual understanding of the Trinity is hazy and remote, we need to remember that the reality of our saving engagement with the Trinity does not depend on our understanding of the doctrine. In fact, the opposite is the case: a believer's understanding of the doctrine of the Trinity is enabled by faithful participation in the life of God in Christ. When we are in the grips of these weaknesses, we also ought to stir each other up to seek fresh awareness and renewed experiences of communion with God the Father (his love and electing), God the Son (his grace and truth as our mediator), and God the Holy Spirit (his indwelling and formation). If there is always the promise of resting in the deep union beneath our acts of communion, there is also the danger of staying in the shallows of our own life and forgetting the abundance on which we stand. In this context, Sibbes warned that "we are only poor for this reason, that we do not know our riches in Christ." (11)

Conclusion

How practical is the doctrine of the Trinity? We should not expect to go to this doctrine to fetch specific ethical commands, or patterns for imitation, or blueprints for human society. If that's what we mean by practical, then no doctrine about God himself will ever be practical in that sense, and least of all the doctrine of the Trinity, which names one of the ways God is unlike us. But the connection of knowledge of God and knowledge of self dictates that we need this accurate, Trinitarian understanding of God in order to walk faithfully. And the dynamic of union and communion shows how the Trinitarian depth of Christian existence supports and funds the daily conduct of our Christian lives.

French pastor Adolphe Monod (1802-1856) had a special regard for the doctrine of the Trinity,a truth he called "most practical and most tender." He preferred to preach the doctrine straight from Scripture, because God's word is the best guide to the heart of what Trinitarian theology is all about. On his deathbed, Monod gave one final sermon about the Trinity, in which he said,

There we find the basis of the Gospel, and those who reject it as a speculative and purely theological doctrine have therefore never understood the least thing about it; it is the strength of our hearts, it is the joy of our souls, it is the life of our life, it is the very foundation of revealed truth. (12)