What Is Orthodox Christianity? The Essential Beliefs That Define the Christian Faith

Christianity and Other Religions — Part 1 of 12

The word Christian is used broadly today.

It can describe a person who attends church every Sunday, someone who identifies with Christianity culturally, or a religious movement that uses the name of Jesus while teaching something very different about who He is.

That raises an important question:

What actually makes Christianity Christian?

Historic, orthodox Christianity is not defined merely by admiration for Jesus, belief in God, conservative morality, or the use of Christian language. It is rooted in specific truths revealed in Scripture about God, Christ, humanity, salvation, and the Church.

These convictions are not theological accessories. They stand at the heart of the Christian faith.

Understanding orthodox Christianity therefore gives us a necessary foundation for evaluating any church, teacher, or religious movement that claims the Christian name.

The First in a 12-Part Series on Christianity and Other Religions

This article is the first in a 12-part ChurchDex series examining Christianity and other religions and belief systems.

Before comparing Christianity with Islam, Judaism, Hinduism, Buddhism, Mormonism, Jehovah’s Witnesses, Christian Science, Unitarian Universalism, New Age spirituality, and secular humanism, we need to establish the standard of comparison.

What does historic Christianity actually teach?

That question is especially important because religious differences are not always obvious. Some belief systems openly reject Christianity. Others use words like God, Jesus, salvation, church, and even Christian while assigning those words meanings that differ substantially from historic Christian teaching.

Throughout this series, we will compare beliefs carefully rather than relying on labels. We will ask the same foundational questions again and again:

Who is God? Who is Jesus Christ? What is our ultimate authority? What is wrong with humanity? How can sinners be reconciled to God? And what hope is there beyond death?

The goal is not to mock people of other faiths or turn theological disagreement into hostility. Christians are called to speak truth with love (Ephesians 4:15) and to give a reason for our hope “with gentleness and respect” (1 Peter 3:15).

But respect does not require pretending contradictory beliefs are the same.

Before we examine the differences, we need to understand the faith against which those differences will be measured.

What Does “Orthodox Christianity” Mean?

In this context, orthodox means right belief—the essential doctrines Christians have historically confessed because they understand them to be taught by Scripture.

This is different from using Orthodox to refer specifically to the Eastern Orthodox Church.

Historic Christian orthodoxy includes Christians across different traditions who disagree about important secondary matters while affirming foundational truths such as the Trinity, the deity and humanity of Jesus Christ, His death and bodily resurrection, and the authority of Scripture.

ChurchDex summarizes that commitment simply: “We are not redefining Christianity. We are reaffirming it.”

That distinction matters.

Christians can disagree about church government, baptism, worship styles, spiritual gifts, and other significant questions without necessarily abandoning Christianity itself. But some doctrines concern the identity of God, the person of Christ, and the gospel itself.

Remove those, and Christianity becomes something fundamentally different.

So what are those essential Christian beliefs?

1. Scripture Is the Authoritative Word of God

Christianity begins with revelation, not human speculation.

Christians believe God has spoken and that the Bible is His inspired and authoritative Word.

Paul writes:

“All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness.”
—2 Timothy 3:16 (ESV)

Scripture tells us who God is, what has gone wrong with humanity, what God has accomplished through Christ, and how His people are to live.

This means Christians are not free to reinvent God according to personal preference or cultural pressure.

Our beliefs must be corrected by Scripture rather than Scripture being reshaped to accommodate our beliefs.

This is also why biblical teaching is an essential consideration when evaluating a local church. A faithful church does not merely mention Bible verses. It submits its doctrine, preaching, worship, and life to God’s Word.

2. There Is One God in Three Persons

At the center of Christian orthodoxy is the doctrine of the Trinity.

Christianity teaches that there is one God who eternally exists in three distinct Persons:

Father, Son, and Holy Spirit.

Jesus commands His disciples to baptize “in the name of the Father and of the Son and of the Holy Spirit” (Matthew 28:19).

Christians do not believe in three gods. Nor do Christians believe that Father, Son, and Spirit are merely three roles performed by one divine Person.

There is one God, and the Father is God, the Son is God, and the Holy Spirit is God.

The Trinity can be difficult to comprehend fully, but it is not optional Christian vocabulary. It concerns the identity of the God Christians worship.

That becomes especially important when evaluating religious groups that use Christian terminology while fundamentally redefining God.

3. Jesus Christ Is Fully God and Fully Man

No question is more important to Christianity than who Jesus is.

Historic Christianity confesses that Jesus Christ is not merely a prophet, moral teacher, created spiritual being, or unusually enlightened man.

He is the eternal Son of God who became truly human without ceasing to be truly God.

John begins his Gospel:

“In the beginning was the Word, and the Word was with God, and the Word was God.”
—John 1:1 (ESV)

John then tells us that “the Word became flesh and dwelt among us” (John 1:14).

Jesus lived without sin. He died for sinners. He rose bodily from the grave, ascended, reigns, and will return.

Christianity therefore cannot be separated from the identity of Christ.

A movement may speak frequently about Jesus, quote Him, admire Him, or even include His name in its own name.

But the crucial question remains:

Which Jesus?

If Jesus is redefined as something less than the eternal Son of God revealed in Scripture, the resulting belief system is not simply another variety of historic Christian orthodoxy.

4. Humanity Is Created in God’s Image—and Fallen in Sin

Christianity offers both an extraordinarily high and deeply sobering view of humanity.

Every human being possesses profound dignity because humanity was created in the image of God (Genesis 1:27).

But something has gone terribly wrong.

Scripture says:

“For all have sinned and fall short of the glory of God.”
—Romans 3:23 (ESV)

Our deepest problem is therefore not simply ignorance, lack of education, insufficient self-esteem, political dysfunction, or failure to discover our spiritual potential.

It is sin.

We have rebelled against our Creator and cannot repair that separation through moral improvement or religious effort.

That diagnosis makes sense of why Christianity’s message centers on rescue rather than self-improvement.

We don’t merely need better advice.

We need a Savior.

5. Salvation Is by Grace Through Faith in Christ

The Christian gospel announces something radically different from an attempt to climb our way toward God.

God saves sinners by grace.

Paul writes:

“For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast.”
—Ephesians 2:8–9 (ESV)

Jesus Christ lived the righteous life sinners have failed to live and died a substitutionary death for sin. He rose bodily from the dead, conquering death.

Forgiveness and reconciliation with God are therefore not wages earned through religious achievement.

They are received through repentance and faith in Christ.

This is why the identity and work of Jesus cannot be treated as one spiritual path among many.

Peter proclaimed of Christ:

“And there is salvation in no one else.”
—Acts 4:12 (ESV)

Christianity’s exclusivity ultimately rests on Christianity’s gospel: if Christ alone accomplished what sinners could never accomplish for themselves, then salvation cannot be separated from Him.

6. The Holy Spirit Is God and Is Actively at Work

The Holy Spirit is not an impersonal spiritual force or divine energy.

He is fully God.

Scripture describes the Spirit convicting, regenerating, indwelling, sanctifying, empowering, and sealing God’s people.

Ephesians 1:13–14 describes believers as being “sealed with the promised Holy Spirit,” who is the guarantee of their inheritance.

Christian life therefore isn’t merely an intellectual agreement with certain doctrines.

God transforms His people.

Through the Holy Spirit, Christians increasingly turn from sin, grow in holiness, love God’s Word, serve others, and become more like Christ.

7. Christianity Produces a People: The Church

Christianity is deeply personal, but it was never designed to be private.

When God saves people, He brings them into a people.

Paul tells believers:

“Now you are the body of Christ and individually members of it.”
—1 Corinthians 12:27 (ESV)

The local church is therefore not an optional religious service added to an otherwise independent Christian life.

Faithful local churches gather to worship God, proclaim the gospel, teach Scripture, administer baptism and the Lord’s Supper, make disciples, equip believers for ministry, exercise biblical accountability, and care for one another.

This is one reason doctrine matters so much when choosing a church.

A friendly atmosphere cannot substitute for a false gospel. Excellent music cannot compensate for a distorted Christ. Impressive programs cannot replace faithful teaching.

Church leaders are specifically charged to “hold firm to the trustworthy word as taught” so that they can teach sound doctrine and confront error (Titus 1:9).

Christians need churches where truth is not assumed, hidden, or treated as negotiable.

Not Every Difference Is Heresy

Recognizing the boundaries of Christian orthodoxy does not mean every theological disagreement determines whether someone is Christian.

Faithful Christians have substantial disagreements.

Baptists and Presbyterians disagree about baptism. Churches differ over forms of government, understandings of spiritual gifts, approaches to worship, and interpretations of various secondary doctrines.

Those differences matter and should be studied carefully.

But disagreement about baptism is not equivalent to disagreement about whether Jesus is God.

This distinction helps Christians pursue two virtues simultaneously: conviction and charity.

We should not call every disagreement heresy.

But neither should we call every belief Christian simply because it uses Christian words.

Why These Essential Christian Beliefs Matter

Doctrine can sound abstract until we recognize what is actually at stake.

The Trinity tells us who God is.

The deity and humanity of Christ tell us who Jesus is.

The doctrine of sin explains what is wrong with us.

The cross and resurrection tell us what God has done about it.

Grace tells us how sinners are saved.

And the doctrine of the Church tells us what redeemed life looks like together.

These truths fit together. Alter one fundamentally, and the consequences spread throughout the rest of the Christian message.

That is why discernment matters when encountering churches, teachers, and religious movements—even those using familiar Christian terminology.

The question isn’t simply:

Do they talk about Jesus?

Ask instead:

Who do they say Jesus is? What do they believe about God? What authority defines their beliefs? What do they say is wrong with humanity? How do they say we are reconciled to God?

Those questions reveal far more.

Christianity Is More Than a Label

Historic Christianity makes extraordinary claims.

God has spoken.

Humanity has sinned.

The eternal Son of God became man.

Jesus Christ died for sinners and rose bodily from the grave.

Salvation is God’s gift, received through faith in Christ.

And those Christ saves are called into His body, the Church.

These convictions establish the foundation for the rest of this 12-part series.

In the articles ahead, we will examine some of the most important questions separating Christianity from other major religions and religious movements:

• Christianity vs. Islam: Is Jesus God incarnate or merely a prophet, and was He truly crucified and raised from the dead?
• Christianity vs. Judaism: Is Jesus the promised Messiah and Son of God?
• Christianity vs. Hinduism: Is there one personal Creator, and is salvation found in Christ rather than karma, reincarnation, and liberation?
• Christianity vs. Buddhism: Is humanity’s deepest problem suffering and desire—or sin and separation from our Creator?
• Christianity vs. Mormonism: Do Latter-day Saint teachings about God, Jesus, revelation, humanity, and exaltation agree with historic Christianity?
• Christianity vs. Jehovah’s Witnesses: Is Jesus the eternal, uncreated God the Son, and is God truly Triune?
• Christianity vs. Christian Science: What are the biblical realities of God, creation, sin, suffering, Christ, and salvation?
• Christianity vs. Unitarian Universalism: Can Christianity be reconciled with religious pluralism and the rejection of essential Christian doctrines?
• Christianity vs. New Age Spirituality: Is God our Creator, or is the divine something to be discovered within ourselves?
• Christianity vs. Secular Humanism: Can humanity explain its dignity, morality, purpose, and ultimate hope apart from God?
• Do All Religions Lead to God?: Can contradictory claims about God and salvation all ultimately be true?

As we work through those questions, our purpose will not be to ridicule people, caricature their beliefs, or exaggerate differences.

We want to understand each belief system fairly—and then compare its claims with Scripture.

The central question throughout the series will be straightforward:

Does this belief system teach the same God, the same Christ, and the same gospel revealed in Scripture and confessed by historic Christianity?

That question has eternal significance.

It also has practical significance for the church you choose.

A congregation can have Christian in its name, sing songs about Jesus, quote from the Bible, and use familiar religious language. Those things alone do not establish Christian orthodoxy.

What matters is what that church actually believes and teaches about God, Scripture, Christ, sin, salvation, and the gospel.

That is one reason theological clarity matters when searching for a church.

Christians need more than private theological convictions. We need faithful local churches where God’s Word is preached, the Triune God is worshiped, Christ and His gospel are proclaimed faithfully, believers are discipled, doctrine is guarded, and brothers and sisters live in meaningful Christian community together.

Understanding orthodox Christianity should therefore lead us beyond simply identifying theological error.

It should lead us toward truth, worship, discipleship, accountability, and committed life in a biblically faithful local church.

References

Scripture

• Genesis 1:27
• Matthew 28:19
• John 1:1–14
• Acts 4:12
• Romans 3:23
• 1 Corinthians 12:27
• Ephesians 1:13–14
• Ephesians 2:8–9
• Ephesians 4:15
• 1 Peter 3:15
• 2 Timothy 3:16–17
• Titus 1:9

Additional Resources

• ChurchDex, The ChurchDex Foundational Statement
• 9Marks — https://www.9marks.org/
• The Gospel Coalition — https://www.thegospelcoalition.org/
• Ligonier Ministries — https://www.ligonier.org/

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