WHAT MAKES AN ARGUMENT SOUND?

Bible and Logic — Study 2

Why correct reasoning is not enough if the statements on which it depends are false.

1. Can an Argument Be Logical and Still Be Wrong?

Yes. And this is one of the most important lessons we can learn about reasoning.

Consider these statements:

Premise 1: All birds are animals.

Premise 2: All animals can fly.

Conclusion: Therefore, all birds can fly.

The conclusion follows logically from the two premises.

But is the conclusion true?

No. Ostriches and penguins are birds, and neither can fly.

The problem is not the way the conclusion follows from the premises.

The problem is that the second premise is false.

This argument is valid but not sound.

That distinction matters when we study the Bible.

A teacher may reason correctly from two statements, but if one statement misrepresents Scripture, the argument has not established its conclusion.

Good reasoning cannot rescue a false premise.

2. What Is the Difference Between Valid and Sound?

These two words have specific meanings in logic.

An argument is valid when its conclusion must be true if all its premises are true.

An argument is sound when it is valid and all its premises are actually true.

Notice the difference.

Validity concerns the connection between the premises and the conclusion.

Soundness requires both a valid connection and true premises.

Let's look at two examples.

Example A — Valid and Sound

• All beagles are dogs.

• All dogs are mammals.

• Therefore, all beagles are mammals.

Both premises are true.

The conclusion follows necessarily.

This is a sound argument.

Example B — Valid but Unsound

• All fish are birds.

• All birds are animals.

• Therefore, all fish are animals.

The conclusion is true. Fish really are animals.

And the reasoning is valid.

But the first premise is false. Fish are not birds.

Therefore, the argument is unsound, even though its conclusion happens to be true.

A true conclusion does not prove that the argument used to reach it was sound.

3. How Do We Know Whether a Premise Is True?

This question takes us beyond formal logic.

Logic can tell us whether a conclusion follows from certain premises.

But logic alone cannot tell us whether every premise accurately describes the world or correctly represents a Bible passage.

For that, we need evidence.

When studying Scripture, we must examine:

• What the passage actually says.

• Who is speaking and to whom.

• What the words mean in their context.

• Whether the passage is a command, promise, historical account, parable, prophecy, or another form of writing.

• Whether other relevant passages clarify or qualify our understanding.

Only after establishing what Scripture teaches should we begin constructing arguments from it.

Otherwise, we may build a perfectly valid argument on a misunderstanding.

And that argument will not be sound.

4. A Bible Example: Where Did Christians Meet?

Consider Romans 16:5.

Paul refers to a church meeting in the home of Priscilla and Aquila.

Philemon 2 also mentions a church meeting in a home.

These passages establish an important historical fact:

Some first-century congregations met in private homes.

Now consider this argument:

Premise 1: Every place where first-century Christians met is the only kind of place Christians may use today.

Premise 2: First-century Christians met in private homes.

Conclusion: Therefore, Christians today may meet only in private homes.

The reasoning might appear convincing.

But examine the first premise.

Where does Scripture establish that every recorded meeting place becomes the only permitted kind of meeting place?

The cited passages do not say that.

The second premise is supported by Scripture.

The first premise requires proof.

Without that proof, the argument has not established its conclusion.

Notice that we have not proved the opposite conclusion either.

We have simply demonstrated that a biblical fact and an unsupported rule cannot establish a sound argument.

This is why we must examine the premises before accepting the conclusion.

5. A Hidden Premise Can Change Everything

Not every argument states all its premises.

Sometimes a teacher makes two statements and then reaches a conclusion that depends on an additional assumption.

Consider:

"Jesus and His disciples sang a hymn" (Matthew 26:30).

"Therefore, Christians must sing when they worship."

Does the conclusion follow from that one example alone?

Not necessarily.

To make that argument work, we would need an additional premise, something like:

"Every activity Jesus and His disciples performed on that occasion is required of Christians in their assemblies."

But is that premise true?

And is it really the principle the teacher intends to defend?

Matthew 26:30, by itself, does not establish such a universal rule.

Other passages, including Ephesians 5:19 and Colossians 3:16, may provide relevant teaching about singing.

Those passages deserve their own careful examination.

Our purpose here is not to settle every question about worship.

It is to recognize the danger of hidden premises.

A conclusion may appear to follow from Scripture only because an additional assumption has been quietly inserted into the argument.

When that happens, we should ask:

"What else must be true for this conclusion to follow?"

Then we must examine whether that additional premise is actually established.

6. Can a True Statement Be Used as a False Premise?

Yes, if the statement is changed or given a meaning it does not have.

Consider John 3:16.

The verse teaches that God loved the world.

Now consider 1 John 2:15.

John tells Christians not to love the world.

Suppose someone argues:

Premise 1: God loves the world.

Premise 2: Christians must imitate God.

Conclusion: Therefore, Christians must love the world in the very sense forbidden by 1 John 2:15.

Something has gone wrong.

The word world does not carry the same meaning in these two passages.

In John 3:16, the world refers to humanity as the object of God's love.

In 1 John 2:15, the world refers to the sinful values and desires opposed to God.

The argument changes the meaning of a key expression.

This is called equivocation.

Even if the statements sound biblical, the argument fails because a word is being used in different senses.

We will examine this problem more fully in Study 4.

For now, remember:

A premise must not only quote Scripture correctly. It must also represent Scripture's intended meaning correctly.

7. Did the Apostles Examine Their Premises?

Consider Acts 15.

Some men were teaching that Gentile Christians must be circumcised according to the custom of Moses to be saved (Acts 15:1).

That was a serious claim.

The apostles and elders met to consider the matter.

Peter described what God had done among the Gentiles.

Paul and Barnabas reported the signs and wonders God had performed among them.

James then appealed to the words of the prophets, citing Amos 9:11–12.

Notice the pattern.

The question was not settled simply by repeating a familiar religious position.

The evidence was examined.

The participants considered what God had actually done and what Scripture had said.

They reached a conclusion concerning the Gentiles without requiring them to become Jews.

Acts 15 is not presented as a textbook lesson in formal logic.

But it does illustrate the importance of testing religious claims against the evidence rather than merely accepting inherited assumptions.

8. Does Sound Logic Guarantee Correct Bible Interpretation?

We need to be careful with this question.

A sound argument has true premises and a conclusion that necessarily follows.

Therefore, its conclusion must be true.

That is what sound means in formal logic.

But when interpreting Scripture, we may mistakenly believe that our premises are true.

We may have misunderstood a passage.

We may have overlooked a qualification.

We may have assumed that a statement applies universally when its context limits its application.

So we must distinguish between two things:

An argument that really is sound.

And:

An argument that we believe is sound.

Those are not necessarily the same.

Our confidence does not establish the truth of our premises.

This is why careful Bible study requires humility.

We should be willing to reexamine a premise when someone presents evidence that we have misunderstood it.

That does not mean every interpretation is equally reasonable.

It means we must distinguish what has been demonstrated from what we have merely assumed.

9. Some Objections Worth Considering

Objection: "If a conclusion is true, why should I care whether the argument is sound?"

Because the same faulty reasoning could produce a false conclusion in another situation.

We should want to believe the truth for good reasons.

A true conclusion reached through an unsound argument still needs adequate support.

Objection: "Doesn't every argument depend on assumptions?"

Arguments depend on premises, but premises are not necessarily unsupported assumptions.

Some are established by observation, testimony, historical evidence, or other reliable means.

In Bible study, we must examine whether the premises accurately represent Scripture.

Some basic starting points may require separate defense. We should identify them rather than hide them.

Objection: "What if two people disagree about whether a premise is true?"

Then they must examine the evidence for that premise.

Repeating the conclusion more forcefully will not settle the disagreement.

Nor will calling the other person illogical.

The question is whether the disputed premise can be established.

Objection: "Can someone use a sound argument to prove something false?"

No.

In formal logic, a sound argument has true premises and valid reasoning.

Its conclusion must therefore be true.

If the conclusion is false, then at least one premise is false or the reasoning is invalid.

The argument cannot be sound.

10. Try It Yourself

Examine this argument:

Premise 1: All the apostles were witnesses of the risen Christ.

Premise 2: Paul was an apostle.

Conclusion: Therefore, Paul was a witness of the risen Christ.

Does the conclusion follow?

Yes.

The reasoning is valid.

Scripture also identifies Paul as a witness of the risen Christ (1 Corinthians 9:1; 15:8).

Now examine another argument:

Premise 1: All the apostles were witnesses of the risen Christ.

Premise 2: More than five hundred people witnessed the risen Christ (1 Corinthians 15:6).

Conclusion: Therefore, all five hundred were apostles.

Does the conclusion follow?

No.

Being a witness of the risen Christ does not, by itself, establish that a person was an apostle.

The argument reverses the relationship.

The fact that apostles were witnesses does not mean every witness was an apostle.

The conclusion does not follow from the premises.

11. What Have We Learned?

We have learned that:

• A valid argument has a conclusion that necessarily follows from its premises.

• A sound argument is valid and has true premises.

• A valid argument can still be unsound.

• A true conclusion can be reached through an unsound argument.

• Hidden assumptions must be identified and examined.

• A premise must represent Scripture's meaning, not merely quote its words.

• Our confidence that an argument is sound does not make it sound.

The lesson is simple:

TRUE PREMISES + VALID REASONING = A SOUND ARGUMENT.

But if a premise is false, or the reasoning is invalid, the argument is not sound.

A Final Thought

The Bible student must do more than collect verses that appear to support a conclusion.

We must examine what those verses actually teach.

We must identify any assumptions we have added.

And we must make sure our conclusion follows from the evidence.

This standard applies to everyone.

It applies to the preacher, the scholar, the Bible class teacher, and the person reading this page.

It also applies to the author of this study.

Our goal is not to defend a conclusion at any cost. Our goal is to discover and follow the truth.

Read First. Reason Carefully. Conclude Later.

TEXT B4 TRADITION

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Bible and Logic — Main Study Page

Does That Conclusion Really Follow?

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Review the difference between true statements and valid reasoning.

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Learn to recognize when someone claims more than the biblical evidence actually establishes.

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