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Lord's Days 5–7: The Mediator and Why Only Christ Could Save Us

Rev. C•D•F• Warrington, M.Div.
By Rev. C•D•F• Warrington, M.Div.

Ordained Minister, M.Div.

June 29, 2026

3 min read

catechism
A bridge spanning a vast chasm at dawn, symbolizing Christ as Mediator bridging the gap between God and humanity in the Heidelberg Catechism

After Lord's Day 2 exposes the depth of human sin through the law, and Lord's Days 3 and 4 examine human nature and the justice of God, Lord's Days 5 through 7 provide the answer the catechism's whole structure has been building toward. If we are truly lost, if we truly deserve God's judgment, and if God is truly just — then who can save us? The answer is the theological heart of the Heidelberg Catechism: only a Mediator who is both truly God and truly human, and his name is Jesus Christ.

Lord's Day 5: The Requirements of the Mediator

Lord's Day 5 (Questions 12-15) asks: 'Since, then, by the righteous judgment of God we deserve temporal and eternal punishment, is there any way by which we can escape that punishment and be again received into his favor?' The answer: Yes, but only if the Mediator satisfies three conditions. He must be able to bear God's full wrath on our behalf. He must be able to satisfy God's justice. And he must be able to deliver others from that wrath. No mere human qualifies — human nature is already under condemnation. No angel qualifies — angels are not our kin and do not owe what we owe.

The catechism is firm that God's justice cannot simply be waived. He is not the kind of God who looks the other way. If sin is to be forgiven, it must be addressed — either punished in the sinner or punished in a substitute. The entire logic of substitutionary atonement rests on this premise: that God's justice is real, his wrath is real, and therefore the salvation he provides is not cheap grace but purchased at enormous cost.

Lord's Day 6: The Person of the Mediator

Lord's Day 6 (Questions 16-19) specifies the Mediator's identity. He must be 'a true and righteous man' — sharing our nature so that he can bear God's judgment on our behalf — and also 'more powerful than all creatures,' i.e., truly God, so that his bearing of judgment is not merely a transfer of condemnation from one guilty party to another. Question 18 asks whether anyone meets these requirements: 'Who then is that Mediator, who is at the same time true God, and a true righteous man?' The answer is simple and total: 'Our Lord Jesus Christ, who has been given to us for complete salvation and righteousness.'

The catechism's reasoning is tight: the requirements for salvation define a profile of the Savior, and the profile matches exactly one person. This is not an arbitrary match. The incarnation is not a happy accident but the eternal plan of a God who purposed from before the foundation of the world to redeem his people through a Mediator who would unite divine and human nature in one person.

Lord's Day 7: Faith in the Mediator

Lord's Day 7 pivots from the objective reality of the Mediator to the subjective question of how his work becomes ours. Saving faith is defined as 'a certain knowledge of God's grace toward me personally, and a wholehearted trust.' This is not merely intellectual assent to historical facts but personal appropriation — knowing that Christ's life, death, and resurrection are for me specifically, not for humanity in the abstract. This faith is not our achievement; it is the gift of the Holy Spirit, worked through the gospel proclaimed in Word and Sacrament. Lord's Days 5 through 7 form the theological spine on which the entire remainder of the Heidelberg Catechism rests.

Tags:catechismreformedchristology

Frequently Asked Questions

What do Lord's Days 5–7 of the Heidelberg Catechism teach about the Mediator?

Lord's Days 5–7 of the Heidelberg Catechism argue that because God's justice requires that sin be punished but God's mercy desires to spare the sinner, a mediator is necessary who is both truly human (to bear the punishment owed by humanity) and truly divine (to bear the infinite weight of God's wrath and restore us to God's favor). The catechism asks whether any mere creature could serve as this mediator and answers that none could—neither a human being (already under condemnation) nor an angel (not of human nature) qualifies. Only Jesus Christ, the eternal Son of God made flesh, perfectly satisfies both requirements.

Why does the Heidelberg Catechism insist the Mediator must be truly human?

Question 16 of the Heidelberg Catechism explains that the Mediator must be truly human because divine justice requires that human nature, which sinned, must also satisfy for sin. A payment made by one who is not truly human would not constitute satisfaction for human guilt under God's law. Additionally, only one who is genuinely human can die—and death was required as the penalty for sin. The catechism's argument here draws on Anselm of Canterbury's 11th-century satisfaction theory of the atonement, which insisted that only a God-man (Deus homo) could pay the debt owed by human creatures to an infinite God.

Why does the Heidelberg Catechism say the Mediator must be truly God?

Question 17 of the Heidelberg Catechism states that the Mediator must be truly divine because the weight of God's eternal wrath against sin is so great that no merely human strength could bear it, and because only one who is himself God could deliver others from God's wrath and restore them to righteousness and life. The divine nature of Christ is not merely a helpful addition to the atonement but is essential to its infinite efficacy: only an infinite person can make infinite satisfaction. This argument draws on the Nicene insistence that the Son is 'of the same substance as the Father' and therefore truly and fully God.

How does the Heidelberg Catechism connect the doctrine of the Mediator to the gospel promise?

Lord's Day 7 of the Heidelberg Catechism asks where saving faith comes from and answers that it comes from the Holy Spirit working through the preaching of the holy gospel. The catechism thus moves directly from the need for a qualified mediator (Lord's Days 5–6) to the means by which sinners come to trust in that mediator (Lord's Day 7), tying the objective work of Christ to its subjective application through Word and Spirit. This emphasis on the preached gospel as the ordinary means by which faith is created reflects the Reformation's high regard for preaching as God's primary instrument of salvation.

What historical controversies did the Heidelberg Catechism's teaching on the Mediator address?

The Heidelberg Catechism's insistence that Christ must be fully human and fully divine addressed ongoing controversies inherited from the early church—including Arianism (which denied Christ's full divinity), Docetism (which denied his genuine humanity), and various 16th-century radical reformers like Caspar Schwenckfeld and the Socinians who questioned Christ's pre-existence or deity. The catechism's formulation also implicitly countered Anabaptist Christologies that suggested Christ brought his body 'from heaven' rather than truly assuming human nature from Mary. By grounding the mediator's qualifications in orthodox Chalcedonian Christology, the catechism secured Reformed theology within the mainstream of ecumenical Christian tradition.

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