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Logical Fallacies: What Are They?


Lately, I've gotten a couple of requests from readers to write about logical fallacies in order to help equip them to spot them in discussions and online. I thought that this was a good idea and that it would be a good resource for quick reference for information on logical fallacies, which are very common on the internet.


Last year, I wrote a post called "A Crash Course in Logic." This post introduced logic and a few basic concepts from the field. In that post, I presented logic as the field that describes with symbols and technical terms what we do every day in conversation, just as is also true with mathematics. We also honor God through the right use of logical reasoning, since we are commanded to love Him with our minds, and He is perfectly reasonable and never reasons wrongly.


Similarly, when we reason wrongly, we fail to conform our arguments to God's pattern of reasoning. But that begs the question: what is a logical fallacy? This post will be divided into two sections. First, I will explain what a logical fallacy is and what the kinds of logical fallacies are. Second, I will explain why it is important that we're able to spot fallacies as Christians and apologists.


What is a Logical Fallacy?


Logic is about the pattern of one's reasoning. It is about the connections between propositions. A proposition is the content expressed by a declarative sentence. When I say, "The sky is blue," that declarative sentence expresses the truth of a proposition (namely, the proposition that "the sky is blue"). When propositions are considered together, sometimes those propositions stand in unique relations with one another. Sometimes, new propositions can be derived from that group of propositions. Let me give an example of a simple syllogism (i.e., a form of deductive argument in which the conclusion is drawn from two premises):

  1. If Socrates is a man, then Socrates is mortal.

  2. Socrates is a man.

  3. Therefore, Socrates is mortal.

In this argument, the conclusion "Socrates is mortal" clearly follows from the two premises. Without having been given the conclusion, you could nonetheless derive it from the two premises if they were all that you were given. In fact, this argument follows a rule of valid reasoning called modus ponens. But what happens when the argument fails to conform to a pattern of valid logical reasoning? What happens when the conclusion doesn't follow from the premises? That there is a right way to reason entails that there is a wrong way to reason. If the conclusion follows from the premises according to a correct form of logical reasoning, then the argument is called valid. If the conclusion fails to follow from the premises, then the argument is called invalid.


There are several terms commonly used for invalid reasoning, including invalid and non sequitur. Put simply, a fallacy is a definable example of bad or invalid reasoning. It is "definable" in the sense that there is often a name attached to the type of fallacy it is. There are several common fallacies that you'll see in everyday conversation and discourse (especially on social media), and this series will be devoted to equipping you to see and respond to those fallacies.


There is one more distinction that needs to be made about fallacies. A fallacy can be either formal or informal. A formal logical fallacy is one in which the form or pattern of the argument explicitly marks it as invalid. There are certain recognizably invalid logical forms, such as "negating the antecedent." Using p and q to stand for propositions and -> to stand for the relation between propositions in a hypothetical statement (read "p -> q" as "if p, then q), we can express the form of this fallacy in symbols:

  1. p -> q

  2. not-p

  3. Therefore, not-q

The expression "not-p" is to say that p is negated or that p is not true. So, if the proposition in question is, "The sky is blue," to negate it is to express the proposition that "The sky is not blue." Let's consider the syllogism I used above. We can make a different argument in the form of this logical fallacy:

  1. If Socrates is a man, Socrates is mortal.

  2. Socrates is not a man.

  3. Therefore, Socrates is not mortal.

As you can see, the conclusion doesn't follow from the premises. That Socrates is not a man doesn't at all entail that he isn't mortal. If Socrates were a cat instead, then he'd nonetheless be mortal. The information given in the two premises have no connection with the conclusion, so the argument is invalid.


So, that's a formal logical fallacy. What is an informal fallacy? An informal fallacy is one in which the lack of connection between premises and conclusion is clear but isn't described in terms of a definable form. For formal fallacies, the fallacy can be defined entirely by the form of the argument. For informal fallacies, it can be more difficult to define the fallacy because it's expressed in the context of an argument without an explicit form. Often, informal fallacies are seen in the context of conversation. Let's consider a discussion that you're likely to have with someone if you discuss politics:


Person A: What did you think about the political debate last night?

Person B: Eh, I liked the Republican candidate, but the Democrat was annoying.

Person A: What about his position on healthcare? I thought that it was reasonable enough.

Person B: I can't listen to anything that guy has to say because he is so arrogant. You don't think that?


In this conversation between Person A and Person B, Person A wanted to talk about the policy positions of the Democratic candidate, but Person B wouldn't engage in that discussion. Instead, Person B dismissed whatever the candidate had to say because he perceived the candidate as arrogant. This is an example of an ad hominem argument, or an argument "against the person." An ad hominem argument attempts to refute a person's position by attacking his or her character. The problem is that one's character bears no relevance to his or her position. In order to refute a person's claims, you must refute the claims themselves. This is an informal fallacy, rather than a formal one, because the fallacy is not explicitly attached to the form of the argument itself.


It is important to distinguish between a formal and informal fallacy because the former must be connected to a specific, named invalid form of reasoning, whereas the latter doesn't have to be connected to a named form. This means that informal fallacies can be harder to identify but are more common, since people don't normally make formal arguments in everyday life. With fallacies explained, why is it important for us to be able to identify fallacies as Christians and apologists?


Why is This Important?


I mentioned at the beginning of this post that we honor God through the use of logical reasoning. That is, when we reason rightly, we show that we are committed to loving God with our minds. God never reasons wrongly. This is something that we have to practice by identifying fallacies when we see them. In this sense, as Christians, we must be committed to valid logical reasoning and good arguments. There is no virtue in arguing badly.


As Christians, we also engage in discussion with other Christians daily. There is plenty of disagreement among believers. Some of this disagreement has to do with secondary doctrinal issues that don't affect whether or not Christianity is true. Some of these disagreements are very serious. The church in America is currently engaged in a dispute over critical theory and critical race theory that will have huge implications for the church in the years to come. Other heretical perspectives like the prosperity gospel and the invasion of new-age perspectives into the church are rampant. If we as followers of Christ are not sufficiently equipped for these disputes, we are vulnerable to false teaching, and false teaching is more likely to make its way into the church at large. Logic, including the recognition of fallacies, equips us to formulate good arguments on behalf of the truth and to tear down opposing arguments. I have quoted 2 Corinthians 10:3-6 multiple times on this blog, and I'll do it again here (NASB):

"For though we walk in the flesh, we do not wage battle according to the flesh, for the weapons of our warfare are not of the flesh, but divinely powerful for the destruction of fortresses. We are destroying arguments and all arrogance raised against the knowledge of God, and we are taking every thought captive to the obedience of Christ, and we are ready to punish all disobedience, whenever your obedience is complete."

When those false ideologies and theologies make their way into God's church and begin to affect the flock, we must take action. A solid understanding of logic and fallacies equips us with the weapons and skills we need to wage this form of spiritual warfare with skill and precision.


With respect to secondary issues, the ability to identify fallacies equips us to be able to spot bad argumentation in brothers and sisters in Christ. With gentleness and love, we can then correct bad reasoning in order to cooperatively come to a better understanding of the truth. The principle here is derived from Proverbs 27:17 (NASB):

"As iron sharpens iron, So one person sharpens another."

And, as we sharpen one another in secondary discussions, we are each better equipped to defend the faith when it is attacked. I've used the analogy of sparring to explain this. When two boxers spar, they engage in a kind of "fight" with rules that are intended to ensure that each boxer will not be injured. Sparring trains you for the real fight. Brothers and sisters in Christ are unified in Christ and are to engage in disputes with love and with a mutual desire to seek the truth. In doing this, we are better equipped for the "real thing," those times when we're combatting heresy or defending the faith before an atheist or some other unbeliever. In that way, engaging in debates on secondary issues can be very beneficial for us.


Finally, it's obvious how being equipped to identify fallacies aids us as apologists. As I said, there is no virtue in arguing badly. Many Christians unfortunately take it for granted that just because Christianity is true, any presentation of it easily defeats another worldview. The problem is that even a good and true position can be defended poorly. Christopher Hitchens, the late fiery horseman of the New Atheism movement, often easily overcame Christian debaters who simply defended the Christian faith badly. Yet, when before William Lane Craig (a Christian philosopher, theologian, and trained debater), most agree that Hitchens lost.


Why was Dr. Craig able to succeed where Hitchens failed? First, Dr. Craig was able to, on the spot, interpret Hitchens' claims in order to subject them to critique. He sidestepped Hitchens' tendency to make outrageous statements intended just for an emotional response and instead focused on the content of his claims and arguments. This is a skill that logic trains us to use. Second, Dr. Craig had a firm grasp of logic and was able to spot fallacious reasoning in Hitchens' case, which was flawed in many ways. Third, Dr. Craig was trained in the use of logical reasoning to put forward better arguments. Each of the five arguments in his cumulative case for Christian theism is valid. I would strongly argue that Dr. Craig had honored the Lord more than others who had shared the stage with Hitchens because he was able to put forward the Christian worldview in a way that was logically airtight. As apologists, we look to those like William Lane Craig as exemplars of the practice of apologetics, and a firm grasp of logical reasoning is a necessary part of it.


Therefore, gaining a better understanding of logical fallacies helps us as Christians and apologists. That is it for this post! This series on logical fallacies will be made up of relatively short posts that explicate a single fallacy. This makes it easier to go for them for quick reference and makes them each an easy read.


If you have questions or would like to reach out to me to discuss these things, feel free to comment here or to send me an email or message on Facebook. If this blog has been helpful and interesting for you, feel free to subscribe to be notified of any new posts. Finally, if this post would benefit anyone else, please feel free to share it on social media. Thanks for reading!

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