I read someone recently who wrote, “if you can’t trust a teacher with the Christian doctrine of God, you can’t trust him, period.” This is a welcome cautionary word (see the full emphatically cautionary piece here). Scripture expects the church to place her trust in her teachers, but also to exercise discernment, searching the Scriptures to test what they say and even to censure them as necessary.

Put positively, the considerable methodological value of this statement becomes somewhat more apparent: a sound doctrine of God is a good starting point or controlling point for everything else. It’s a good habit, in other words, to keep the doctrine of God in view as we work our way through the other loci (topics) of systematic theology, because in one way or another each theological doctrine may be thought of as an aspect of the doctrine of God.

‘It’s all about God’ has a nice poetic ring to it; but it isn’t poetry. It is a theological reality that everywhere we look in theology we see the nature of God on display. In everything God does, his particular nature is operative and to some degree manifest, even if only because what God does God does. There is some analogy here with all creatures: when a dog runs, he runs the way dogs run; when a human expresses himself, we learn about the self-expressive habits of human beings and so about the human being itself. A running dog is a demonstration of caninity, or dogginess; a self-expressing man displays aspects of humanity.

The triune God acts ‘triunely’. God is Trinity, one God in three persons, and so whatever God does, He does as one God in three persons. What does that mean? No one can plumb the depths of Trinitarian being and agency, but the doctrine of inseparable operations1 helps here: in every action of God, all the persons are involved. Augustine wrote: “Just as the Father, Son, and Holy Spirit are inseparable, so they work inseparably.”2 The doctrine of inseparable operations is designed to deny dis-unity in God. No act of God relative to creation (ad extra) is the work of one person exclusively or of a sub-portion of the essence (only part of God); God always acts as the one (triune) God. Since God is not separated into persons, but the three persons, equal in deity, subsist in the one God, therefore divine action cannot be separated. Most obviously, tri-theism is thereby disallowed, but beyond that, inseparability as an implication of essential unity prevents such errors as inferring from Jesus’ quotation on the cross from Ps 22:1 a rupture in the essential unity of God, or an ontological disunion of the first and second persons. However we handle the crucifixion and Ps 22, we cannot say that violence was done to the Trinity of God as such. Unfortunately such errors are not uncommon.

But still, in divine action the persons must be distinguished somehow.3 Most conspicuously, the incarnation and mediatorial work of the Son, including his ascension, present reign and promised return—these are Son’s work in particular. Neither the Father nor the Spirit is incarnate and born of Mary, but the Son only. Likewise the subsequent sending of the Spirit and the Spirit’s activity at Pentecost. Acts 2 describes the activity of the Spirit specifically, not the Father or the Son, appearing as tongues of fire and ‘giving utterance’.

So, while affirming the inseparability of operations because of the unity of the Godhead, theologians have used the word “appropriation” to give each person His due in the distinguishability of His activity. Incarnation is ‘appropriated’ to the Son. Another way to honor the distinguishability of persons in divine acts ad extra is, as noted in the second quote from Richard Muller below, by saying that an action “terminates” in one of the persons. When we use either of these theological locutions, we mean that the Son only was incarnate, and that the Son’s incarnation caused no essential disunity in God.

(Actually in this case, Scripture reveals details about the Trinitarian economy: it was the Father’s will to send the Son, and the Son was conceived by the Holy Spirit and upheld by the Spirit throughout his earthly ministry, and now He applies from heaven the redemption accomplished by the Spirit.)

So even in terms of appropriation and the distinguishability of triune personal acts, no one person is ever far from the other two. The point is that in everything God does, God triune does it. And if this is the case, theology ought always to be Trinitarian.

In revelation, in making Himself known, the Father, the Son, and the Spirit act as one, and apart from voluntary, divine self-revelation there would be no knowledge of God. Notice that this entails dizzying circularity: we always and only know God triune because God only reveals as God triune. The revealing God is triune; the self-revealing activity of God is triune; and so our knowledge of God is everywhere triune, even if triunty is always mysterious to the creature.

In John 14:1, Jesus makes two statements. The first is this: “Let not your hearts be troubled.” This word of consolation and encouragement comes toward the end of Jesus’ earthly ministry. He will soon be arrested, tried, and executed. Knowing that his crucifixion is imminent, and that his death will be followed soon after by violent persecution of the church, he seeks to equip His disciples with courage for perseverance. Calvin writes of this verse:

Not without good reason does Christ confirm his disciples by so many words, since a contest so arduous and so terrible awaited them; for it was no ordinary temptation, that soon afterwards they would see him hanging on the cross; a spectacle in which nothing was to be seen but ground for the lowest despair. The season of so great distress being at hand, he points out the remedy, that they may not be vanquished and overwhelmed; for he does not simply exhort and encourage them to be steadfast, but likewise informs them where they must go to obtain courage; that is, by faith, when he is acknowledged to be the Son of God, who has in himself a sufficiency of strength for maintaining the safety of his followers.4

Jesus immediately adds this: “Believe in God; believe also in me.” Connecting this with the prior statement of encouragement, Augustine says that Jesus “comforts them by affirming Himself also to be God.” “For it follows as a consequence,” argues Augustine, “that if ye believe in God, ye ought to believe also in me: which were no consequence if Christ were not God.” Augustine writes that it is as though Jesus had said, “You are afraid of death as regards this servant form; ‘let not your heart be troubled,’ the form of God will raise it again.”

Like this, it preaches, no doubt. But if we bring verse 1 together with the subsequent verses, the prominence of Trinity as both the subject and content of divine self-revelation takes center stage.

Thomas asks about “the way” to where ever Jesus is going, to the place where Jesus goes to prepare a place for His disciples. Although Thomas isn’t fully aware of it, he has asked about the way to blessed, eternal communion with God. And Jesus responds: “I am the way.”

Why is Jesus “the way” to eternal communion with God? Because, he says, “No one comes to the Father except through me.” Put it together and we see that Jesus is preaching, in hints minimal but explosive, a message of encouragement, based on the faithfulness of God, and centered approaching the Father in confidence through the Son.

“Believe also in me” and especially “I am the way, the truth, and the life” together indicate that Jesus is sufficient for true and saving knowledge of God. Jesus is not only the “way,” he is also the “truth,” and consequently or summarily “the life.” So, the way to communion with God, to the truth about God, and to blessed life eternal—these are found in Christ. To be precise, these are not things which are found in Christ; He Himself in His own person is these things. Christ himself is the way, the truth, and the life.

“No one comes to the Father except through me” indicates that Christ is not only sufficient, as noted, but uniquely necessary for true and saving knowledge of God unto life eternal. That is, truth and life are found in Christ and in Him only. This is clear in the gentle admonition in verse 7 (“If you had known me, you would have known my Father also”), and Jesus waxes memorably even more explicit when responding to Philip’s question in the next section: “Whoever has seen me has seen the Father.”

This statement is striking in so many ways. Consider first the point of view of the author of Hebrews:

“Long ago, at many times and in many ways, God spoke to our fathers by the prophets, but in these last days he has spoken to us by his Son” (Heb 1:1-2)

It becomes clear as the epistle unfolds that the author is set on defending the supremacy of Christ over the revelation and redemptive events of OT history. Jesus Christ is the fullness of redemptive work and history. The author focuses at one point on Moses himself, the towering prophet and deliver of Israel, arguing that:

“Moses was faithful in all God’s house as a servant, to testify to the things that were to be spoken later, but Christ is faithful over God’s house as a son” (Heb 3:5-6)

Jesus, too, sets himself up as greater than Moses, as representing a fuller redemptive moment than Moses, the arrival of what was merely foretold during Moses’ day. John the Baptist said of Jesus, “He who comes after me ranks before me, because he was before me” (John 1:15; also 27, 30), and Moses would have said the same. Jesus was before Moses, and even before Abraham (John 8:58), but He was greater than both. According to Jesus, this is in fact what the Mosaic Scriptures teach:

“There is one who accuses you: Moses, on whom you have set your hope. For if you believed Moses, you would believe me; for he wrote of me. But if you do not believe his writings, how will you believe my words?” (John 5:45-47; also Luke 24:27, 44-48)

Jesus here affirms striking continuity between Himself and the testimony of Moses, and even between Himself and the efficacy of the redemption of God during Moses’s day. There is continuity, but also a surpassing supremacy. Abraham rejoiced that He would see the day of Jesus, and Moses wrote about Christ (John 8:56; 5:46).

Moses met with God face to face, as a man meets with a friend (Ex 33:11). After meeting with God, Moses’ face shone brightly (Ex 34:29-35). Here in John 14 (esp. verses 1, 6-7, 9), Jesus says that the glory of His own person and His relationship to the Father are such that anyone who “believes in Him” sees the Father in Him. Moses’s face shone with derivative glory, as the moon reflects light original to the sun; but Jesus has his own glory, equal to the glory of God the Father (John 1:14; 17:5; Col 1:15-17). Jesus is equal in power and majesty to God the Father (Rom 9:5; Phil 2:6; 1 John 5:20).

And the Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father [μονογενοῦς παρὰ πατρός5], full of grace and truth (John 1:14)

In Moses the Israelites had a prophet who had met face to face with God; in Jesus they themselves could look upon, with their very own eyes, the exact imprint of his nature, the full deity of God dwelling bodily (Heb 1:3; Col 2:19). This is nothing less than unequivocal affirmation of the full deity of the second person, the same Son who is now incarnate.

So, the emphasis of Hebrews is on the redemptive historical significance of the experiential immediacy of the arrival of the Son of God in the flesh and on His mediatorial finality. Hebrews 1:1-3 captures all this succinctly. But the discussion in John 14 features a different emphasis: Jesus’ rebuke of religious speculation—not merely as factually shaky or incomplete, but as unrighteous and unacceptable to God. Calvin transposes Jesus’ concern thus:

 . . . Satan interposes clouds of every description to hinder us from contemplating God. The consequence is, that our faith, seeking God in his heavenly glory and inaccessible light, vanishes away; and even the flesh, of its own accord, suggests a thousand imaginations, to turn away our eyes from beholding God in a proper manner.

When Jesus answers Thomas, he encourages him to seek communion with God through and in Himself, the Son, and He issues a gentle corrective in response to Thomas’s wondering dullness. Then when Jesus answers Philip, His patience for Philip’s wandering mind runs thin: “Jesus said to him, ‘Have I been with you so long, and you still do not know me, Philip? . . . How can you say, ‘Show us the Father’?” (John 14:9). In the earlier exchange we see a gentler invitation to the love of God in the grace of the Son; in the subsequent one we see a pointed rebuke of seeking God anywhere else but in the Son. Calvin put it in certain terms:

Wherefore all theology, when separated from Christ, is not only vain and confused, but is also mad, deceitful, and spurious

There is no question that in the early verses of John 14, Jesus declares His own equality to the Father, but also the distinctness of His person (14:1b) and His mediatorial privilege (Acts 4:12; Eph 4:5). But his emphasis is on true knowledge of God unto life—truth and life which can be found only in the Son.

The implications for unregenerate knowledge of God, the knowledge of God claimed by unbelievers or non-Christians of any sort, are worth noting, as well. If Jesus here groups together the way to the Father, the truth about God, and life, then he distinguishes these from their complements: enmity with God; lies, suppression, and foolishness; darkness, suffering, and death. And these He groups together, too.

We say that there is Christian belief and all else is idolatry. But notice that in these verses from John 14, there are only Christians with Jesus, even His inner circle, the disciples themselves. So Jesus’ warnings here are directed at the church. His concern here is not full blown idolatry and overt rejection of the one true God, but methodological wolves from among us (Acts 20:29). His concern is purity within the body. To put it another way, Jesus is concerned both that Christian belief is faithful—orthodox, we might say—but also that it is intolerant of corruption and compromise within the church itself. So Paul makes clear: “for there must be factions among you in order that those who are genuine among you may be recognized” (1 Cor 11:19). Nor is Paul ashamed to declare false teachers—not only false teaching, but even the teachers themselves—“anathema” (Gal 1:8). And Jesus, who says “I have not come to bring peace but a sword,” has come “to set a man against his father, and a daughter against her mother, and a daughter-in-law against her mother-in-law. And a person’s enemies will be those of his own household” (Matt 10:34-36).

The point to emphasize is this: all of this hinges on believing in God the Father almighty, confessing the full eternal deity of the Son, and approaching God only by the Spirit of adoption on account of the mediatorial grace of the Son incarnate, God among us, without sin but like us in every way. So Augustine, once more:

“Believe in God, and believe in Him, who, by nature and not by robbery, is equal with God; for He emptied Himself; not, however, by losing the form of God, but by taking the form of a servant.”


1 From Richard Muller’s Dictionary of Latin and Greek Theological Terms: Opera Trinitatis ad extra sunt indivisa: The external or ad extra works of the Trinity are undivided; specifically, since the Godhead is one in essence, one in knowledge, and one in will, it would be impossible in any work ad extra . . . for one of the divine persons to will and do another [work ad extra].

 2 Quotations from Augustine are from his Tractates on the Gospel of John, no. 67.

3 From the same entry in Muller’s dictionary: Sometimes the Protestant scholastics will speak of the opera ad extra as opera certo modo personalia, personal works after a certain manner, because the undivided works ad extra do manifest one or another of the persons as their terminus operationis, or limit of operation. The incarnation and work of mediation, e.g., terminate on the Son, even though they are willed and effected by Father, Son, and Spirit.

4 Quotations from Calvin are from Calvin’s commentary on John 14.

5 The term monogenes has been at the subject of heated controversy in recent years. One recent and very substantive contribution can be found here.