I’d Like to Have an Argument, Please

Author Greg Koukl Published on 07/01/2023

To celebrate Stand to Reason’s 30th anniversary, we’re republishing classic issues of Solid Ground that represent some of the foundational ideas characterizing our work over the decades—ideas that continue to be vital to apologetics and evangelism today.

I want to teach you how to assess a basic argument. How can you know if a line of thinking is a good one or not?

There’s no magic to this. The tools of thinking are simple ones. Anyone can employ them skillfully with a little practice. If you have the right equipment, you can make a lot of progress, even if you don’t consider yourself an intellectual whiz-kid.

Think of an argument like a simple house, a roof supported by walls. The roof is the conclusion and the walls are the supporting ideas. In the lingo of logic, the walls are called premises and the whole structure of the building is called a syllogism.

When all the details of a syllogism are in proper working order, the conclusion can be trusted. The walls are strong enough to support the roof, so the whole structure is reliable. It rests securely on its supporting foundation.

Here are two well-worn syllogisms you may have heard before:

  • All men are mortal.
  • Socrates is a man.
  • Therefore, Socrates is mortal.


  • If it’s raining outside, then the streets are wet.
  • The streets are not wet.
  • Therefore, it’s not raining outside.

Here are some popular ways those two different forms of argument have been employed in defending theism. The first is called the Cosmological Argument, and the second is an example of the Moral Argument:

  • Everything that begins to exist has a cause.
  • The universe began to exist.
  • Therefore, the universe had a cause.


  • If God does not exist, then objective morals do not exist.
  • Objective morals do exist.
  • Therefore, God exists.

The goal of critical thinking is to look at any line of reasoning and test it. Are the walls solid, or can they be knocked down? If the walls go down, the roof goes flat, and the argument is defeated.

A House with No Walls

First, an observation. Some arguments are not really arguments at all. In terms of our house illustration, people sometimes try to build their roof right on the ground. Instead of erecting solid walls—the supporting ideas that hold up the conclusion—they simply assert their conclusion and pound the podium.

An argument, though, is different from an assertion. An assertion simply states a point. An argument gives reasons showing why the point should be taken seriously. These reasons become the topic of mutual discussion or analysis. If there are no reasons, there’s little to assess. Opinions are opinions, not proof. A mere point of view cannot be taken seriously as worthy of belief. That requires reasons.

A roof is useless when it’s on the ground. In the same way, an assertion without evidence is not reliable. The untutored may be persuaded, but those thinking more carefully will not be swayed.

I frequently get calls on the radio from people who think they’re giving me an argument, when all they’re doing is forcefully stating a point of view. They sound compelling, but a closer look reveals an emperor with lots of attitude but no clothes. My first task is to recognize that the roof is lying flat on the ground and simply point it out. The caller wants a free ride, but I won’t give it to him. He must ante up, and good reasons are the price of admission for thoughtful discussion.

If you find yourself stymied in a conversation, you may be looking for an argument that’s not there. Ask yourself, “Did they give me an argument or just make an assertion?” If the latter is true, then say, “That’s an interesting opinion. Now I have a question: How did you come to that conclusion? Why should I believe what you just told me? Can you give me any good reasons for your view? What, specifically, is your argument?”

Don’t let challengers flatten you by dropping a roof on your head. Make them build walls underneath their roof. Ask for reasons or facts that support their point of view.

Three Ways an Argument Can Go Bad

Any real argument—as opposed to a mere contention—has three elements. First, it has a particular form. Second, it makes particular claims. Third, it uses particular words or terms to make its point. When an argument goes bad, the problem is with the form, or the claims, or the terms.

First, an argument’s form can be bad. Take this syllogism: “All men are cheerful. John is a man. Therefore, John is cheerful.” This is a simple argument containing two statements (premises) and a conclusion. The conclusion is dependent on the strength of the first two statements. The first is the major premise—all men are cheerful. The second is the minor premise—John is a man. The final statement is the conclusion—John is cheerful.

Notice the form of this argument. Given that all men are cheerful and that John is a man, the conclusion is inevitable. It follows from the premises because the form is correct in this case. When an argument is structured properly like this, we say the argument is valid.

What about this one: “All men are cheerful. Jane is not a man. Therefore, Jane is not cheerful.” A moment’s reflection shows this doesn’t work. Even if it were true that all men are cheerful and Jane is not a man, it still wouldn’t follow that Jane is not cheerful. Women can be cheerful, too. This form is not valid.

We use the term “fallacy” to describe an argument that has a faulty construction. There are different types of fallacies listed in logic books, and I won’t detail them here. Many of them, though, are obvious upon careful reflection.

When the form is bad—when the conclusion does not follow from the premises—it’s called a non sequitur, Latin for “it does not follow.” Non sequiturs cannot be trusted. It may turn out that Jane is not cheerful, but you can’t draw that conclusion from the argument as it stands.

Even when the form is right, there still may be problems. Claims can also make an argument go bad. Accurate form (a valid argument) does not guarantee that the statements themselves are true. Following our house illustration, the architectural structure may be solid, but the wood itself could be rotten. What if it’s not true that all men are cheerful? Maybe some are gloomy. What if John is not a man, but your neighbor’s pet schnauzer?

Take this argument: “All unicorns live in Ireland. Pegasus is a unicorn. Therefore, Pegasus lives in Ireland.” Acknowledging that the form is valid (it is) doesn’t at the same time commit you to the existence of unicorns or tell you anything about where they live. The factual questions about unicorns is a separate issue.

If the claims in the statements are false, then the argument still fails even though the form is right. Clear thinking requires we look closely at the claims as well as the form. The statements themselves must be true.

The following argument is an example of this mistake: “When an alleged historical account is similar to a myth that came before it, then the later account is also a myth. Ancient myths of dying and rising redeemers are remarkably similar to the Jesus story. Therefore, the Jesus story is also a myth.”

Though the argument is valid (the form is correct), it fails because neither of the premises is true. Myths of alleged dying and rising redeemers that predate the time of Christ bear little resemblance to the accounts of Jesus we find in the Gospels. Further, even if they did, this wouldn’t prove the details of the life of Jesus were fictions. That must be determined independently on historical grounds.[1]

The third way an argument can go wrong is in its terms. The same words may mean different things in different parts of the syllogism. This is called an “equivocation.” Equivocation means a vagueness, ambiguity, or uncertainty. If somebody states her opinion very clearly and then, under challenge, becomes less sure of her position, we say she’s equivocating. She waffles; she’s uncertain.

Sometimes words themselves are equivocal. They have multiple meanings that become confused with each other in the discussion. This creates problems for an argument.

Look at this example: “All men are cheerful. John is a man. Therefore, John is cheerful.” The form is in order and, for argument’s sake, let's stipulate that the claims are true. Is our conclusion reliable? That depends.

What if it turns out that the word “man” in the first premise refers to grown males, while the same word in the second premise refers to an adolescent male? Once the terms are clarified, the argument looks like this: “All adult males are cheerful. John is an adolescent male. Therefore, John is cheerful.” See the problem? This argument falters through equivocation.

Here’s a theological example: “Jesus is God. Mary is the mother of Jesus. Therefore, Mary is the mother of God.”

The form here seems correct—the conclusion follows from the premises. It also seems that the individual statements are true. But something’s wrong here. God is not the kind of being that has a mother. Where did we go wrong?

The problem becomes more obvious when we take it a step further: “Mary is the mother of God. God is a Trinity. Therefore, Mary is the mother of the Trinity.” This, of course, is patently false. But why is there a problem if the form is sound and the claims are in order?

The trouble lies with the terms. There’s an equivocation here on the clause “Jesus is God” in the first syllogism. Jesus is a very unusual individual. Yes, he is God, but he’s also fully human. Jesus is one person with two natures, the nature of God and the nature of man.

When we say Jesus is God, we are not saying his humanity is divine. That would be a contradiction. We are saying he is God in that he has a divine nature. Mary is the mother of Jesus in the sense that she’s the mother of his humanity. She is the mother of his human nature, not his divine nature.

Equivocation—lack of clarity—on these terms makes a false conclusion seem sound. The claims are right. The form is right. But the conclusion is false because the meanings of the terms are equivocal.

Once, I took a call on our radio show from a Jehovah’s Witness who argued, “Jesus is God. God is a Trinity. Therefore, Jesus is a Trinity.” The argument was valid in form, but since the conclusion was clearly false, he argued, the problem must be in the premises.

My caller thought he had logically disproved the Trinity. Either Jesus is not God, or God is not a Trinity. His attempt failed through equivocation, though, but the problem is difficult for most to see at first. It has to do with the troublesome word “is.”

There are at least five meanings for the word “is.” Resolving the equivocation in this argument requires distinguishing between the “is” of essential predication (“Aristotle is human”) and the “is” of identity (“Aristotle is the author of the Nichomachean Ethics”). There are also the parts/whole “is” (“Aristotle is skin and bones”), the “is” of accidental predication (“Aristotle is white”), and the “is” of existence (“Aristotle is”).

When Christianity teaches that Jesus is God, it doesn’t mean that Jesus and God are exactly identical. Jesus is different from the Father. He shares the Father’s essential nature, but he is not everything that God is. God subsists in three persons; Jesus is only one of those persons.[2]

The missing element here was an explanation of terms. Once the meanings were clarified—and the equivocation removed—this attack on the Trinity was defeated.

Part of the assessment of an argument is based on the clarity of the concepts involved. This is why precision with words is so important for clear thinking.

Invisible Walls

Sometimes it’s difficult to assess an argument because the full form of the argument is not stated. The elements are not listed one, two, three as they are in the examples above. Some of the parts are taken for granted—“understood” by the participants—in the process of conversation. This streamlines conversation, but it can also allow faulty claims to go undetected. Let me illustrate.

Once, a homosexual said to me, “Jesus never condemned homosexuality.” Though this is only a single sentence, it’s actually a full argument in shorthand, streamlined for brevity. The conclusion didn’t need to be stated. I got the point. I was wrong for attacking homosexuality on moral grounds. Because Jesus never condemned homosexuality, it is therefore morally acceptable behavior.

Notice, though, that the conclusion is not the only thing taken for granted here. The minor premise is stated, and the conclusion is assumed, but what of the major premise, our first step in the argument? The unspoken major premise—the invisible wall holding up this argument—contained a serious flaw that went undetected.

We can determine if this is a problem by asking what kind of major premise is needed to make this argument work. The full argument would have to look something like this: “Whatever Jesus did not explicitly condemn is morally acceptable. Jesus never explicitly condemned homosexuality. Therefore, homosexuality is morally acceptable.”

The form of this argument is good; nothing amiss here. But look closer at the major premise. It seems this statement is clearly false. It’s not true that whatever Jesus didn’t directly condemn is morally acceptable. Jesus never explicitly condemned slavery, child abuse, wife-beating, or even gay-bashing, for that matter, but this proves nothing about his moral opinion on those issues.

Many Christians are caught flat-footed here, sensing something is wrong but not knowing what it is. Sometimes we have to look more closely to identify the unspoken premise before we can see the problem clearly. In this case, that can be done by making the invisible wall visible.

Ask a simple question: “Are you saying that if Jesus doesn’t specifically condemn something, then he condones it?” When they back off (and they must, because such a view is untenable), you might ask, “Then what’s your point?” Don’t get into a fuss. Just ask the question calmly and directly. The silence that follows proves the game is up.

A Jehovah’s Witness once called me and said, “The Trinity isn’t mentioned in the Bible.” The unspoken conclusion was obvious: The Trinity is not biblical. But that conclusion depended on the strength of an invisible wall, which I asked about next.

“Are you saying that anything not specifically mentioned in the Bible cannot be truly biblical?” He was in trouble here because lots of things aren’t mentioned specifically in the Bible that still find support in Scripture. The word “monotheism” isn’t in the Bible, for example, but clearly the idea is taught there.

“No,” he answered.

“Then what’s your point?” I responded, and the argument was over.

Often the flaw in an argument—the “fact” that’s wrong—is hidden in an unspoken assumption your challenger takes for granted. Kick the invisible premise into the open. Often it’s all that’s needed for the whole structure to come tumbling down.

The Obligation of Reason

To assess a genuine argument and not a mere assertion, examine the structure. Observe the form of the argument. Examine the claims. Look for hidden statements that may not have been expressed. Finally, examine the terms to see if there’s any equivocation, any ambiguity or lack of clarity that might influence the outcome.

If the argument is sound—if the form is valid, the claims accurate, and the terms clear and precise—then the conclusion is going to be true. Period. In fact, the conclusion is irrefutable; it’s not even possible to be mistaken.

This demonstrates the compelling nature of rationality. There is a bomb-proof quality about deductive logic. If one is faced with a logically valid argument with clear terms and accurate claims, he has a rational obligation to believe the conclusion, even if he doesn't like what he finds. This is called intellectual honesty.

Rationality has nothing to do with what we like; it has to do with what is true. That’s why careful thinking is an indispensable tool for all who are interested in knowing the way the world really is, for those who really do love truth.


[1] For more details, see Gregory Koukl, “Jesus, Recycled Redeemer?Solid Ground, September/October 2009, 

[2]In this case, it can be truly said that the outcome of the argument depended on what “is” is.


[Article updated on 7/01/23.]