Informal Fallacies of Logic

I'm trying to finish up a chapter on logic in the philosophy textbook today and thought I would write some about informal logical fallacies here.

Appeal to Force (argumentum ad baculum)
It should be obvious that forcing someone to hold a certain position does not make that position true. The law usually will reject a confession from a suspect that has been coerced out of them. Force is the stuff of power and politics, but it is not the stuff of logic. You cannot change what is logically true by torture or pressure.

Appeal to Emotion (argumentum ad populum)
Debbie Boone famously sang a song called, "You Light Up My Life." One of the lines says, "It can't be wrong, 'cause it feels so right." Whatever merit this thought might have in other contexts, it has no merit at all in logic. Whether or not something is true or not logically has nothing to do with feelings or emotions.

Closely related to this is the fallacy of subjectivism.<2--in> Something is not true or false logically because of what I want to be true or false. For example, the question, "Does God exist objectively, apart from human thinking?" has nothing to do with whether I like the idea of God or whether it works for me. It is not a matter of my motivation to believe or disbelieve.

The question of whether God exists objectively depends on, well, whether or not God exists objectively. To be sure, you can find conceptions of God out there that do both believe God exists and that this belief is a matter of human subjectivity. But this is not the kind of existence we were asking about--whether a Being exists apart from human thinking and the actions to which that thinking leads. If this sort of God exists, then God exists regardless of my feelings or desires.

Appeal to the Majority
If the fallacy of subjectivism is the idea that something is not logically true or false because of your individual desires, then it is similarly true that something is not logically true or false simply because a majority of individuals want it to be true or false. In general, truth or falsity in logic is not a matter of vote. Whether or not an idea is true or false is a matter of, well, whether it is true or false.<3>

Is it raining right now outside in the normal sense of what it means to rain? The answer to this question is not a matter of a vote. Either it is literally raining or it is not.<4>

Appeal to Improper Authority
In this and the next fallacy, we shift to slightly different logical ground, namely, when bringing other people into arguments makes sense and when it does not. In some circumstances, it might make sense to put weight on a person's claims because of who they are. Take a victim of a crime who is mentally stable, knew his or her attacker, has no apparent ulterior motives, and observed that person attacking him or her. This person certainly seems a credible authority on who made the attack. This credibility does not prove guilt absolutely, but it may prove beyond reasonable doubt.

In many cases, however, it is clear that we rely on the opinion's of many individuals who are not really an appropriate authority on an issue, not least ourselves. "Everyone's entitled to their opinion." But that does not mean that everyone's opinion is equally valuable or likely to be true.<5> Informed opinion is, at least logically, more valuable than an individual's whims and fancies.

This fallacy becomes a real issue in matters of religion and politics. For example, is a person who can quote Bible verses an authority on what God thinks on a particular issue? Frankly, is knowing a Bible verse even the same as being an authority on what that verse meant when it was written down--as well as what God wants us to think of it today? Does being able to quote Bible verses make one an authority on world events and matters of contemporary science? It seems doubtful.

Argument against the Person (ad hominem)
An often effective technique in debate is to attack the person you are debating rather than the actual issue at hand. Politics is rife with this sort of slight of hand. So and so is in a picture with this other so and so. So and so cusses a lot or had an affair with so and so. So and so is a liberal or a conservative or a communist or a Fascist or unpatriotic.

But logically, you cannot dismiss the truth of an idea by attacking the person who holds the idea. Whether or not an idea is true or false depends on, well, whether or not the idea is true or false. It does not depend on the person who has the idea. In the Bible, Satan knows that Jesus is the Son of God (e.g., Matt. 4:6), and demons themselves believe in the one God (James 2:19).

Two related falacies are the genetic fallacy and the circumstantial fallacy. The genetic fallacy is to say that something must be false because of the reasons they came to the idea. Freud famously suggested that people believe in God because they want a Father figure to take care of them. Marx famously called religion the "opiate of the masses." But even if these things proved to be true in many cases--that people believe in God because they want divine help or to make life bearable--that would not logically disprove the existence of God. Whether or not God exists depends on, well, whether or not God exists.

The circumstantial fallacy argues against a person's position by pointing out the circumstances in which the person is making the claim. "Isn't it true that the District Attorney has cut you a deal if you will testify?" It may be true, but that does not logically necessitate that the witness is lying.

For this reason, circumstantial evidence is of varying value in a trial. From a practical standpoint, it can actually be very compelling. Let's say I find my son with cookie crumbs and chocolate smears around his mouth, a trail of crumbs leading back to a cookie drawer that is opened, with a box of cookies opened and standing upright in the drawer. I did not actually see my son take or eat the cookie. I am not an eyewitness to the "crime." Nevertheless, it is reasonable to infer that he in fact has just eaten a cookie from the drawer.

At the same time, this circumstantial evidence does not logically prove that he did. He could have been framed by one of his clever sisters, without him even realizing it. For that matter, space aliens or a mischievious angel might have set the whole thing up. This scenario gives us a good illustration of the difference between what is logically necessary and what is possible or even probable.

Appeal to Ignorance
Sometimes someone will argue that because you have not or cannot prove one thing to be true, that the opposite must be true. "Prove it. You can't prove I did it." Of course the fact that I cannot prove that you did something has nothing to do with whether you did it or not. Either you did it or you did not, and my ability to tell does not affect anything. Christians of course believe that God knows.

Perhaps one of the instances of this fallacy of greatest interest to Christians is when it is applied to God. You cannot prove that God exists and, therefore, God must not exist. This argument hardly makes any logical sense at all. It is true that an individual may believe they have no reason to believe in God. But this fact does not in any way serve as a proof that God does not exist.

Hasty Generalization
Next to fallacies involving subjectivism, perhaps the most frequently committed logical fallacy is that of "hasty generalization." You draw an inference when you simply do not have enough information to do so. In fact, this fallacy often accompanies the committing of other fallacies, such as the fallacies of composition and division that follows.<6>

Fallacies of Composition and Division
The fallacy of composition is when you assume that something is true of a whole group of things simply because it is true of some of things within it. We see this fallacy at work in what sociologists call in group/out group dynamics. People tend to pick positive individuals or traits from the groups to which they belong and then ascribe these particular characteristics to the whole group. Similarly, we tend to pick negative traits or examples from other groups we do not like and paint the whole group with the same brush.

By contrast, the fallacy of division is when you take something that is true of the whole and then apply it to all of its parts. The fact that a team loses a ball game does not mean that every individual on the team played poorly or worse than those on the other team. The fact that an administration as a whole makes bad decisions does not mean that everyone in that administration agreed with those decisions or thought them the best course of action.

After This, Because of This (post hoc propter hoc)
Another frequent expression of hasty generalization is the assumption that because something happened after something else, the first thing must have caused the second thing. For example, let's say I touch your ear lobe and then you immediately fall over dead. It might be tempting to think that the touch had something to do with you dying, but it is not at all a logical certainty.

We especially have to be careful about this fallacy when we are looking at historical events and trying to ascribe praise or blame for things. A related fallacy is confuse something that correlates with a trend for the cause of that trend (non causa pro causa). Let's say that a large plant closes in a small town and in the next year, both the crime rate rises and a large number of people move out of town. It is of course possible that the rise in crime is causing people to leave town. But it is perhaps even more likely that the rise in crime more correlates with the people leaving town, both primarily because of the factory closing.

Fallacy of Diversion
The fallacy of diversion involves a changing of the real subject at hand. Some of the fallacies we have already mentioned can serve such a diversion, such as attacking the person instead of his or her position. One common form of diversion confuses the consequences of something with the value of that thing. For example, it may very well be that prohibiting certain drugs will result in a sub-culture of illegal drug making and trafficking. This fact does not necessarily mean, however, that we should not prohibit those drugs. The abuse of something does not clearly invalidate that thing.

Another form of diversion is a straw man argument. In this fallacy, you create a portrait of your opponent's position that looks a little like it but is actually not quite the same position. Most of us would have a hard time beating up your average weight lifter or wrestler. But we could probably vanquish quite easily a version of them stuffed with straw. In the same way, it is easy to dismiss someone else's argument when he or she is not in the room... and you are misrepresenting their position.

Fallacy of Equivocation
The fallacy of diversion involves a change of subject. The fallacy of equivocation changes the sense of the words you are using in mid-argument. Take the famous quip, "Can God make a rock so big that He cannot lift it?" The person who poses this question usually wishes to argue that it does not make sense to say that God is all powerful.

But this person has mixed up two distinct concepts associated with the word can. One has to do with power or ability and the other has to do with possibility. Christians do not normally suggest that it is possible for God to do everything, for everything includes things that contradict themselves. Christians believe rather than God has all power.

The answer to the question, "Can God make a rock so big that He cannot lift it?" is thus "no" precisely because God is all powerful. God can (has the power to) lift any rock. He can (it is possible for Him to) lift any rock. He cannot not be able to life any rock. The question is worded in a way that plays into the hands of the fallacy of equivocation.

False Alternative
Another fallacy is to present an either/or option, when in fact other alternatives exist. Either you love me or you hate me. Either you favor the war or you do not. Life is seldom this simple. If you do not believe every word of the Bible is true then you do not believe any of the Bible is true. If you believe in evolution then you do not believe God created the world. We can believe that every word of the Bible is true and not believe in evolution and yet recognize that the last two sentences are examples of the fallacy of false alternative.

For example, there are Christians who believe that God created the world through evolution. They may be wrong, but they represent another possibility for which the either/or sentence above did not allow. And if for some strange reason someone believed that Lot's wife actually turned into mustard rather than salt (Genesis 19:26), that would not imply that they did not believe in the resurrection or that we should love our neighbor.

One notable example of the fallacy of false alternative is a slippery slope argument. A "slippery slope" is the idea that if you start down a certain path, you will not be able to stop. If you let kids go out on dates unsupervised, they will all end up having sex. Now in real life, slippery slopes can actually have some substance to them. Most parents who do not want their teenage children having sex do not leave them alone in their bedrooms with a girlfriend or boyfriend and then leave for the night. But logically, it is not an absolute certainty that one thing will lead to another. Other alternatives exist.

Begging the Question (Circular Reasoning)
A final fallacy we might mention is begging the question, which is when you assume your conclusion in your argument. We can believe the Bible is inspired and recognize that we cannot 2 Timothy 3:16 to prove it: "all Scripture is God-breathed. You are assuming the Bible is inspired in your attempt to prove that the Bible is inspired. This would be like saying "Ken never lies because he told me he never lies." What if I turn out to be a flagrant liar?

A related fallacy is the complex question, such as in some cases when a lawyer leads a witness. "When did your anger issues stop?" You are assuming that the person had anger issues. The question thus asks a follow up question when you haven't yet established the answer to the first one, namely, "Did you have an anger problem?"