“Go therefore and make disciples of all nations, baptising them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you.”
Given the opportunity to strengthen a recent convert in the Christian faith, where would you begin?
Our Lord’s Great Commission provides an answer. Jesus commands His church to make disciples, baptising them into the one name of the Father, the Son, and the Holy Spirit. The Trinity is therefore not an advanced doctrine reserved for theologians. It stands at the entrance of the Christian life. Every believer is baptised into the name of the Triune God, worships the Triune God, prays to the Father through the Son by the Spirit, and receives salvation from the Father through the Son in the Spirit.
Christian discipleship is rooted in the confession of one God in three distinct persons: Father, Son, and Holy Spirit—equal in deity, eternal in being, undivided in essence, yet personally distinct.
As disciple-makers, we must both construct and dismantle. We build believers up in the knowledge of Christ (), while demolishing arguments raised against the knowledge of God (). We teach what Christians must believe, but we must also equip them to recognise teachings that distort the identity of the God they worship.
For help in this task, we turn to one of the great disciple-makers of the early church: Irenaeus of Lyons.
A Manual of Essentials
Irenaeus was a second-century bishop and theologian who devoted much of his ministry to defending the apostolic faith against various forms of Gnosticism. In The Demonstration of the Apostolic Preaching, he addressed a Christian named Marcianus, writing to confirm him in the faith and provide what he called “a manual of essentials.” The work is not merely an argument against error. It is a compact presentation of the biblical storyline—from creation to Christ, and from Christ to the promised resurrection.
Where does this seasoned pastor begin?
He begins with God—not with an abstract supreme being, but with the Father, the Son, and the Holy Spirit.
Drawing upon , Irenaeus describes the Father as the One who is over all, the Son as the One through whom all things were made, and the Spirit as the One who dwells in God’s people and conforms them to His likeness. He then presents the basic structure of Christian faith:
one God, the Father and Creator of all;
the eternal Word and Son of God, through whom all things were made and who became man for our salvation;
the Holy Spirit, who spoke through the prophets and renews humanity unto God.
For Irenaeus, this was not speculative theology. It was “the foundation of the building”—the truth into which Christians were baptised and by which their entire lives were ordered. The Father grants regeneration through the Son by the Holy Spirit; the Spirit leads us to the Son, and the Son brings us to the Father.
There is no hidden deity behind the Father, Son, and Spirit. God is eternally Triune. The Father is God, the Son is God, and the Holy Spirit is God; yet they are not three gods, but the one living and true God.
This is the God Christians confess.
What Is Heresy?
Before examining Irenaeus’s categories, we must define our terms carefully.
Not every theological error is heresy. Christians can misunderstand a secondary passage, disagree over church government, or reach different conclusions concerning the timing of Christ’s return without abandoning Christianity. Even serious errors should not automatically be described as heretical.
Heresy is the persistent denial or corruption of truth essential to the identity of God, the person and work of Christ, or the Gospel by which sinners are saved.
It is not merely an opinion we dislike. It is teaching that overturns the Christian faith while continuing to claim its name.
This is why the apostles speak so severely about those who preach another gospel, deny the Father and the Son, or refuse to remain in the teaching of Christ ( ). Such teaching does not merely weaken Christian maturity; it removes the foundation upon which Christianity stands.
At the conclusion of his Demonstration, Irenaeus groups false teaching under three recurring denials:
inventing another Father or God besides the Creator;
rejecting the Son and the reality of His Incarnation;
refusing the Holy Spirit and the prophetic truth He has given.
These three categories remain remarkably useful.
The Father: Do Not Invent Another God
The Gnostic teachers opposed by Irenaeus frequently distinguished between the Creator revealed in the Old Testament and a supposedly higher, previously unknown deity. According to them, the material world was not the good creation of the Father but the defective work of an inferior being.
Irenaeus answered by insisting that the Father of Jesus Christ is the same God who created the heavens and the earth, spoke through the prophets, formed humanity in His image, called Abraham, delivered Israel, and promised the coming Messiah.
There is no higher God above the Creator. There is no hidden deity behind the Father. The God who said, “Let there be light,” is the God and Father of our Lord Jesus Christ.
This remains a necessary boundary. Any teaching that presents the Father as one deity among many, as a being who developed into godhood, or as something less than the eternal Creator has abandoned the biblical doctrine of God.
For example, official Latter-day Saint teaching distinguishes the Father, Son, and Holy Ghost as separate divine beings and has taught that the Father was once a mortal man who progressed to godhood. Whatever Christian vocabulary may accompany such beliefs, this is not the one eternal and uncreated God confessed by Scripture and historic Christianity.
The Christian confession is uncompromising:
“Hear, O Israel: The LORD our God, the LORD is one.”
The Father is not one god within a larger society of gods. He is the eternal, uncreated source of all things, who eternally begets the Son and, with the Son, breathes forth the Holy Spirit. He does not grow, progress, learn, or change. He is the One “from whom and through whom and to whom are all things” ().
The Son: Do Not Diminish or Divide Christ
The person of the Son has been contested throughout the history of the church.
Some have denied His full deity. Arius taught that the Son existed before the world but was nevertheless created and therefore not equal or co-eternal with the Father.
Others denied His genuine humanity. Various Gnostic and Docetic teachers claimed that Christ merely appeared to possess a human body or that the divine Christ temporarily inhabited the man Jesus. But a Christ who only appears human cannot truly suffer, obey, die, or redeem humanity.
Still others have confused the Son with the Father. Modalism teaches that Father, Son, and Holy Spirit are not eternally distinct persons but temporary manifestations or roles assumed by one divine person. In this view, God is sometimes Father, sometimes Son, and sometimes Spirit.
Each error destroys part of the Gospel.
If the Son is not fully God, He cannot reveal the Father perfectly, bear the infinite weight of divine judgment, or bring us into communion with God. If He is not fully human, He cannot represent us, obey in our place, suffer for our sins, or raise our humanity into everlasting life. If He is not personally distinct from the Father, then the Father did not send the Son, the Son did not pray to the Father, and the Father did not glorify the Son.
The biblical Christ is one divine person with two complete natures—fully God and fully man.
He is the eternal Word who was with God and was God, through whom all things were made (). Without ceasing to be what He eternally was, He became what He had not previously been: truly human (). The Son did not surrender His deity but assumed our humanity.
Modern forms of these ancient errors remain. Jehovah’s Witness teaching, for example, explicitly describes Jesus as a created being rather than Almighty God. Oneness Pentecostalism, by contrast, confesses Christ’s deity but denies the eternal personal distinction between Father, Son, and Holy Spirit, describing them as ways in which the one divine person reveals Himself.
Irenaeus directs us back to the apostolic Christ: the eternal Son of the Father, truly incarnate, crucified in the flesh, raised bodily from death, and reigning forever.
“Whoever has seen me has seen the Father.”
Jesus can say this not because He is the Father, but because He is the perfect image and revelation of the Father—the eternal Son who shares the same divine nature.
The Holy Spirit: Do Not Reduce Him to a Force
Errors concerning the Spirit are often less immediately recognisable, but they are no less serious.
The Holy Spirit is not an impersonal energy, emotional atmosphere, or power that Christians learn to manipulate. He is a divine person who speaks, teaches, wills, intercedes, grieves, searches the depths of God, distributes gifts, and glorifies Christ (; ; ).
When Ananias lied to the Holy Spirit, Peter declared that he had lied to God (). The Spirit possesses not merely divine power but the divine identity.
The fourth-century Macedonian error denied the Spirit’s full deity, reducing Him to a subordinate creature or ministering power. Similar teaching continues wherever the Spirit is treated as merely God’s impersonal force. Jehovah’s Witness publications, for example, explicitly identify the Holy Spirit as God’s “active force” rather than a divine person.
But there is another way the Spirit is dishonoured: claiming His authority while disregarding the Word He inspired.
The Holy Spirit carried the prophets and apostles as they spoke from God (). He does not contradict Himself. Therefore, any supposed prophecy, revelation, vision, or spiritual experience that corrects, supplements, or overturns the apostolic Gospel cannot have come from Him.
This does not mean that every Christian disagreement about spiritual gifts is heresy. Faithful Christians differ over whether certain gifts continue and how they should function. The dividing line is crossed when someone claims divine authority for teaching that opposes or surpasses Scripture.
The Spirit’s ministry is not to draw attention away from Christ or to establish new objects of faith. Jesus said:
“He will glorify me, for he will take what is mine and declare it to you.”
The Spirit reveals the Son, applies the Son’s work, conforms believers to the Son’s image, and brings them through the Son to the Father.
The Trinity Is the Shape of Salvation
The doctrine of the Trinity is not an intellectual puzzle added to the Gospel. It is the very shape of the Gospel.
The Father purposes salvation and sends the Son.
The Son assumes our nature, obeys in our place, bears our judgment, and rises from the dead.
The Holy Spirit unites us to Christ, gives us new life, produces faith, dwells within us, and seals us for the inheritance to come.
The Father does not die upon the cross. The Spirit does not become incarnate. The Son does not send Himself. The persons act according to their personal distinctions, yet every work of God toward creation is the undivided work of the one God.
Our salvation is therefore from the Father, through the Son, by the Holy Spirit.
This is why denying the Trinity eventually distorts salvation. A false god produces a false gospel. If we do not know who God is, we cannot rightly understand what He has done to save us.
Disciple-Making in the Triune Name
Irenaeus teaches us something essential about Christian discipleship: new believers need more than encouragement and practical advice. They must be grounded in the identity of the God who has saved them.
We should teach them to confess:
the Father as the eternal Creator and source of salvation;
the Son as fully God and fully man, crucified and risen for sinners;
the Holy Spirit as the divine person who gives life and sanctifies the church;
the unity of the divine essence;
and the real distinction of the three persons.
We must also prepare them to recognise counterfeits. Yet our defence of the Trinity should never become merely combative. The goal is not to produce Christians who can identify every heresy while remaining cold toward God. The goal is worship.
The Triune God is not merely to be analysed, but adored.
The Father has loved us and chosen us in Christ.
The Son has given Himself for us.
The Spirit has poured God’s love into our hearts.
Therefore, let us learn from Irenaeus how to place an arm around a younger Christian, unfold the excellencies of the Father, Son, and Holy Spirit, and establish that believer firmly within the apostolic faith.
For this is eternal life: to know the Father through the Son in the power and fellowship of the Holy Spirit.
“The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all.”
Notes:
1. Irenaeus, The Demonstration of the Apostolic Preaching, 3, 6–7, 99–100.