The Trinity and the Christian Life: Why the Truth about God Demands Undivided Devotion

Some years ago, two pastors from a Reformed Baptist Church in St. Charles, Illinois, hosted a podcast titled “Doctrine and Devotion.” The conviction that drove the podcast was that doctrine must always lead to devotion. Belief necessarily affects behaviour.

Scriptural truth about God always aims to shape the life of his people. We have taken some time, if only at a surface level, to consider how the Bible affirms the historic Christian doctrine of Trinity. But if doctrine must lead to devotion—if belief must affect behaviour—we must ask, how should trinitarian teaching shape the way we live? We have already explored some of this, but here I want to think more fully about this question.

We began our consideration of the Trinity by exploring Paul’s reaffirmation of the Shema in 1 Corinthians 8. His teaching there arises from instruction concerning a very practical issue: whether Christians may eat food sacrificed to idols. Rather than simply giving the right answer, he offers theology, which should guide his readers to the appropriate answer. The principle is straightforward: What we believe about God determines how we live before God.

If, as Paul affirmed, there is one God, our worship must be undivided. If there is one Lord, our allegiance must be exclusive. A right understanding of God will lead to right living before God. Conversely, distorted or shallow views of God inevitably produce distorted living.

The principle, therefore, is simple: If “there is no God but one,” and if “there is one God … and one Lord, Jesus Christ,” we cannot have a heart of divided loyalty.

In Corinth, believers were tempted to treat idols as insignificant and therefore harmless. In many modern translations, the phrases “an idol has no real existence” and “there is no God but one” are placed in quotation marks. Translators believe that these were catchphrases employed by the Corinthians to justify certain behaviour. In this case, while their claim that there is only one God and that idols are nothing were theologically accurate, they were using this sound theology to mistreat one another.

Corinthian believers who felt freedom to eat food offered to idols were tempted to disregard the weaker consciences of those who did not enjoy the same freedom. Those who were hesitant to eat were in danger of either despising those who were free, or of ignoring their own conscience by eating since—if they admitted that idols were nothing.

But while idols have no real existence, a weaker believer eating food offered to idols, by virtue of his troubled conscience, would engage in divided loyalty. For him, eating was a genuine spiritual threat. If there is one true God, worship cannot be shared. Devotion cannot be split. Allegiance cannot be divided.

While believers today in Western-influenced cultures may not be tempted to bow to carved images, the reality of idolatry has not disappeared. It simply looks different.

In every age and every culture, there are rival “gods” competing for the loyalty of the human heart. For some, idols may take the form of success, approval, comfort, pleasure, security, or power. For others, it may be offering undue allegiance to ancestors, religious experiences, or even gifted teachers. Idols promise identity, fulfilment, and meaning. But they cannot deliver what they promise, because they are not God.

Paul’s words remain as relevant today as they were in ancient Corinth. There may be “many gods and many lords” in the eyes of unbelievers, but Christians know that there is only one.

To confess “one Lord, Jesus Christ” is to recognise that he is not one authority among many—he is the authority. He is more than someone to admire or learn from—he is the Lord to whom we must submit. He defines our identity. He directs our decisions. He commands our obedience. He receives our worship. There is no area of life that lies outside his authority.

Paul’s language in v. 6 gives us a framework for the Christian life: We exist for the Father and through the Son. This means that our lives are oriented toward God as our ultimate goal, and sustained by Christ as our mediator.

We do not live for ourselves but for our Father. We do not approach God in our own strength but through the Son. This shapes everything. Our worship is directed to the Father. Our access is through Christ. Our life is sustained by Christ. The Christian life is, at its core, a God-centred and Christ-dependent life.

Essentially, this passage confronts the divided heart. It is possible to confess the truth about God with our lips while living as though other “gods” hold our loyalty. We may affirm that there is one God, yet functionally live for many.

Paul calls us back to a clear and exclusive confession: one God, one Lord. This calls for repentance—not only from obvious sin, but from misplaced trust and misplaced devotion. We must forsake anything that claims the loyalty that belongs to God alone.

The doctrine of the Trinity is not confined to theological statements—it shapes the rhythm of the Christian life. We pray to the Father, through the Son, by the Spirit. We worship the one God—Father, Son, and Holy Spirit. We live in dependence on Christ and for the glory of God. This is not abstract theology. It is the lived reality of knowing God.

Ultimately, Paul’s teaching leads us to worship.

If there is one God, who is the source and goal of all things, then he is worthy of our entire lives. If there is one Lord, through whom we exist, then he is worthy of our complete devotion.

Worship is not confined to a moment or a place. It is the offering of our whole lives to God. As Romans 12:1 puts it, we should “present [our] bodies as a living sacrifice, holy and acceptable to God, which is [our] spiritual worship.”

The question this passage leaves us with is both simple and searching: Who truly has your allegiance?

Both in what you say and in how you live, who defines you? Who directs you? Who receives your trust, obedience, and worship? For the Christian, the answer is clear: the one God, the Father, and one Lord, Jesus Christ.

To confess this truth is to live it. It is to turn from every rival and give yourself wholly to God. It is to trust in Christ as the one through whom you have life. It is to order your life around the glory of the one for whom you exist. This is the call of the gospel. This is the shape of the Christian life.

And as we live in the light of this truth, we bear witness to the reality that there is indeed one God—Father, Son, and Holy Spirit—worthy of all honour, all obedience, and all praise.