Philosophical Theology

I. The Trap of “Simple Faith”

It is a comforting truth of the Christian faith that a person can be saved without a deep understanding of complex doctrines. The thief on the cross is definitive proof that the minimum requirement for salvation is simple, childlike trust in Jesus Christ (Luke 23:42–43). As the Westminster Confession of Faith teaches, saving faith is the work of the Spirit of Christ in the heart (WCF 14.1), and the smallest measure of this faith is no less saving than a mature faith (WCF 14.3).

Indeed, many beloved saints throughout history have lived and died with relatively simple theological understanding. Surely, God has saved and used countless believers who could not articulate the hypostatic union or the distinction between justification and sanctification, yet who loved Christ sincerely and tried to walk faithfully with him. However, a spiritual trap often grows out of this comforting truth. The mistake is simply this: If I can be saved without knowing a specific doctrine, then that doctrine isn’t necessary or valuable for my Christian life.

This pragmatic thinking creates a severe imbalance. It overemphasizes how we are saved (by faith alone) at the expense of who makes salvation possible (Christ alone). When we overemphasize the act of believing, we easily neglect the specific identity of the Savior and the logic of salvation. While a simple faith is entirely saving, an untaught faith remains fragile. To grow in deep assurance, we eventually have to look past our own act of believing and gaze at who Jesus actually is and how salvation is possible. The stability of our Christian faith depends on understanding how the Savior can be both truly God and truly man and why this union of natures is necessary for salvation. Without this understanding, the believer’s gaze is misdirected inward toward how well they are believing, rather than outward toward whom they have believed (2 Timothy 1:12).

Although believers do not need to master complex theological concepts like the “hypostatic union” to be saved, this objective truth of orthodox Christology is what gives the cross its saving power (1 Timothy 3:16). As believers internalize profound truths regarding the wisdom of God in Christ, they grow in spiritual maturity, transitioning from simple faith to deep doctrinal stability (Ephesians 4:13-14). A consistent, coherent theology that answers difficult questions builds an unshakeable assurance of salvation. In the end, a well-grounded and theologically informed faith leads to a more abundant Christian life, one that can more fully glorify and enjoy God (WSC Q&A 1) than it otherwise would.

II. Building the Foundation: How Our Beliefs Hold Together

To understand how theology builds assurance, we must distinguish between consistency and coherence.

• Consistency means there are no contradictions within a specific belief. For example, it is consistent to believe that “Jesus is both God and man” (Romans 1:3–4) and that “Jesus died for sinners” (Romans 5:8). Separately, these statements contain no internal contradictions. They can peacefully coexist in a person’s mind. 

• Coherence goes one step further. It is the presence of interdependence. Coherence shows how different doctrines work together and actually require one another. It explains why separate, consistent statements belong to the same theological system.

When our theology lacks consistency, we suffer from spiritual unease because we feel we are standing on shifting sand. (Arminianism, with its understanding of human cooperation, can create doubt rather than settled assurance.) When our theology lacks coherence, our faith feels like a collection of unrelated and isolated bits, rather than a fully integrated, unshakable worldview (Heidelberg Catechism Q&A 15–18). (Certain strands of Evangelicalism can feel theologically fragmented by offering a collection of emphases that do not always cohere into a unified system of doctrine.)

While consistency keeps our beliefs from collapsing, and coherence binds them together, it is explanatory power that gives theology its greatest pastoral strength. An internally robust system of doctrine is valuable, but until it can explain how and why the gospel works, it will be less than reassuring. In other words, explanatory power is the ability of doctrine to show why salvation actually works, not just that it is true. This is exemplified in the doctrine of the hypostatic union (Jesus as one person with two distinct natures), though other deep doctrines aid in this service.

III. Lessons from the Past: When Theology Breaks, Peace Fails

Church history shows that when a theological system loses its consistency, coherence, or explanatory power, believers suffer a crisis of assurance.

• The Loss of Consistency: In the late medieval church, theologians tried to teach that salvation is a free gift of grace, but also that humans must take the first independent step to release that grace. This contradiction drove people into absolute despair and agonizing doubt. The system told people to trust grace, but forced them to ask, “Have I done enough to release or earn that grace?” Theological contradiction destroys gospel peace.

• The Loss of Coherence: In the fourth century, the Arians argued that Jesus was a created being, not God. While they could consistently say that Jesus died for sinners, the system lacked coherence. A created being cannot bridge the gap between God and man, nor bear infinite wrath. By destroying the coherence between who Jesus is and what Jesus did, the system stripped believers of any real security. This is why the “Jesus is all that matters” approach fails, and why the Westminster Confession 8.2 insists that the Son of God is “of one substance and equal with the Father.”

• The Loss of Explanatory Power: In the early church, Apollinaris taught that Jesus had a human body but a purely divine mind, effectively replacing the human intellect with the divine Logos. While it may have sounded pious, it stripped the theology of the cross of its ability to explain how the totality of a human being can be saved. If Christ did not possess a human mind, he could not redeem it. If this system were true, it could not offer peace to believers suffering from an anxious mind, intrusive thoughts, or intellectual guilt. Without the explanatory power of a fully human Christ, the system left the believer’s conscience exposed and unredeemed.

IV. The Power to Explain: Why the Cross Actually Works

Explanatory power is the ability of our theology to make sense of how salvation actually works. When our theology answers the deep questions of salvation, it silences the intellectual doubts that the enemy uses to attack assurance (2 Corinthians 10:5). We can see this clearly through three specific realities of the cross, which redeem the early church’s inconsistency, incoherence and befuddlement discussed above.

• Sustaining the Human Nature (Redeeming the Medieval Dilemma): The medieval crisis of assurance assumed salvation depends on a fragile human step to “release” grace. Explanatory theology destroys this inconsistency by showing that salvation is entirely a work of divine power. On the cross, Christ’s divine nature upheld his human nature (in the unity of his person), allowing him to fully endure and exhaust God’s judgment without being destroyed (Heidelberg Catechism Q&A 17; Westminster Larger Catechism Q&A 38-40). Because the divine nature guaranteed the success of the human nature, the work is finished. Accordingly, there is no human step left to take, completely resolving the plaguing doubt of “have I done enough?

• The Value of a Three-Hour Sacrifice (Redeeming the Arian Dilemma): The Arian system lacked coherence because a created being cannot bridge the gap between God and man, nor bear infinite wrath. The cross solves this through the infinite value of the Savior. How can a finite, three-hour crucifixion substitute for an eternity in hell for billions of people? Apart from the hypostatic union, this calculation fails. But because the person dying on the cross is the infinite God (Acts 20:28), Christ’s suffering possesses infinite value. The infinite dignity of the Second Person infuses a transient act with eternal significance, perfectly bridging the infinite chasm that a created Arian savior never could.

• The Redemption of the Mind (Redeeming the Apollinarian Dilemma): If Christ did not possess a fully human mind alongside his divine mind, as Apollinaris falsely taught, our own fallen intellects would remain unredeemed. As the early church recognized, “whatever Christ did not assume, He did not redeem.” Because Jesus took on a real human intellect (Luke 2:52), our secret thoughts, intellectual failures, and mental foibles were fully redeemed at the cross. This provides absolute peace to the believer suffering from the anxiety of guilt. Our feeble faith is saved!

V. Modern Missteps: The Anxiety of the Performance Checklist

When a church system loses its consistency and coherence, assurance fades away. Consider a modern evangelical church whose official doctrinal statement says salvation is the gift of God. Yet, its functional culture belies grace (e.g., certain sermon applications, small group metrics that impose demands, false spirituality and unbiblical accountability). The believer is bombarded with unbiblical benchmarks. Is your quiet time long enough? Is your worship passionate enough? Are you volunteering for enough ministries? Are you “on fire” for Jesus? This work-oriented mindset can lead someone to measure personal salvation by performance, like when the useful discipline of devotions becomes an end in itself, eclipsing a methodical pursuit of a theological framework through which daily devotions can be understood unto greater edification (Acts 8:31). Accordingly, prioritizing a theological framework need not diminish the value of personal devotions; rather, it rescues them from becoming a tool for self-justification and restores them as a source of genuine edification. It also can reorient the believer to a deeper appreciation for the pulpit ministry of the word.

Consistency breaks down when formal theology says you are saved by Christ’s mediatory work, but the implicit message within the church’s culture is you must earn God’s favor. This Galatian error of beginning in the Spirit but seeking perfection by the flesh is a theological contradiction that forces believers into morbid introspection, toward despair. Joy and peace evaporate when a system praises free grace with its mouth but inadvertently measures salvation by a checklist of religious activity, standing in stark contrast to Galatians 3:3.

VI. Shifting the Focus: From Our Performance to His Perfection

The only way to break this bewitching spell that fosters a going-through-the-motions Christian life, is to turn our attention away from self and toward a deep study of God and his works. In doing so, we fix our minds on an object of contemplation entirely outside ourselves, One that transforms us as we behold him.

VII. Final Thoughts: The Anchor for an Anxious Conscience

Deep theology is not an intellectual dessert reserved for professors in ivory towers; it is a practical necessity for the growing, ordinary Christian.

As the saying goes, “right thinking is necessary for right feeling.” So, as the Westminster Confession of Faith 18.2 affirms, true assurance is not a bare conjectural or probable persuasion, but an “infallible assurance of faith founded upon the divine truth of the promises of salvation.”

When a Christian understands not just that they are saved, but the biblically grounded theology that informs them of how they are saved, their assurance shifts from a fragile and emotional “hope so” to an objective and rooted “know so.” By pursuing a theology of consistency, coherence, and explanatory power, we do not complicate our faith; rather, we solidify it!

VIII. Closing With Additional Faith-Building Theological Concepts For Further Study

The hypostatic union is one of many profound realities that stir wonder in the heart of the believer. Alongside it stand many essential doctrines that offer a consistent, coherent, and explanatory framework for the faith once delivered to the saints. Below are some for further study and reflection.

Active Obedience: Christ perfectly fulfilled God’s moral law. This righteousness is credited to believers, allowing them to stand faultless before God relative to the demands of this law. Scripture: Romans 5:19, Galatians 4:4-5, Matthew 3:15

Passive Obedience: Christ voluntarily accepted the penalty of the law by suffering and dying on the cross. His death satisfies God’s justice and removes the guilt of sin by receiving the Father’s wrath. Scripture: Philippians 2:8, Romans 5:8, 1 Peter 2:24, Romans 3:25

Penal Substitutional Atonement: Christ took the legal place of sinners, vicariously bearing the penalty they deserved. God executed punishment upon a perfect substitute rather than bypassing sin. Scripture: Isaiah 53:5-6, Galatians 3:13, 2 Corinthians 5:21, 1 Peter 3:18

Eternal Generation of the Son: The Son is eternally begotten of the Father, sharing the exact same divine essence without beginning or end. This confirms the Son is co-equal and co-eternal with the Father. Scripture: John 1:1-2, John 1:14, John 1:18, Hebrews 1:3

Perichoresis (Mutual Indwelling): The Father, Son, and Holy Spirit mutually indwell one another in eternal communion without their personalities being blended. This ensures that when believers see and are united to Christ, they truly see and are united to the Father. Scripture: John 10:30, John 14:9-11, John 17:21

Inseparable Operations of the Trinity: Because the three Persons share one divine essence and will, they act as one in creation, providence and grace. The work of the cross was not the Father punishing an unwilling Son, but a unified act of Triune love toward believers. Scripture: John 5:19, Genesis 1:1-3, Ephesians 1:3-14, Hebrews 9:14