SkepticReport * The Logical Fallacies In The Face Of Rationality

September, 2003
Preface

The ability to reason, plus other physical attributes, is no doubt what sets human beings apart from other animals, and what has given them the privilege to becoming the dominant species on Earth. Observation, experimentation and correct reasoning are the basis of knowledge, which so much has improved the quality of life of people and other beings.

But we not always reason correctly. History shows us how often people have reasoned incorrectly in their effort to understand the world and gather knowledge. And in our daily lives we are constantly making mistakes in our reasoning line.

We often find ourselves in a situation where we have to state or defend a position by means of arguments, or to analyze arguments of others in debate. How can we decide whether a given argument is correct?. When confronted with several arguments, how can we decide which one is better or at least the most plausible?. How can we identify an argument as erroneous?

In the present article we will examine some useful tools to analyze the validity of a given argument, or better yet, to recognize when an argument is poor, weak or plain wrong. These tools are called "Logical Fallacies".

The process of analyzing the validity of an argument is not, in general, an easy one. Some mental abilities and skills acquired through practice, plus a strict logical way of thinking, are needed traits. Some of the fallacies we will examine are easy to recognize, while others are more subtle and difficult to grasp. It is even possible that discrepancies arise on whether a given argument is fallacious or not.

The present article is not, and does not pretend to be, a comprehensive, formal or academic document on the matter. Readers interested in a more profound treatise on the subject may refer to the many references available. A Google search for "Logical Fallacies" is recommended as a starting point.

Definitions of terms

Premise, Conclusion: Statements, that can be either true or false
Argument: Conjunction of premises leading to a conclusion. Here the argument is the whole set of premises plus the conclusion. For an argument to be correct, neither the premises nor the conclusion need to be true.
Reasoning: Mental process by which an argument is constructed
Logical Fallacy: Error in reasoning which invalidates an argument, either totally or partially.

As an example, let's consider this little correct argument: "When it rains the sky is cloudy, and now it's raining. Therefore, the sky is cloudy". Here we have: Premise 1: "When it rains the sky is cloudy"; Premise 2: "It's raining"; Conclusion: "The sky is cloudy".

Logical fallacies

Argument from Ignorance

Also known as "Argumentum ad Ignoratiam" in Latin. This fallacy takes place when assuming that because something has not been proven false, it must be true.

It's quite common among the proponents of the paranormal, occult and supernatural, and also among those faithful believers in God.

Examples:

""As nobody has been able to prove that UFOs don't exist, they must exist"
"I believe in God, and if you don't, then… prove me that he doesn't exist!""

A retrospective look at history shows how erroneous this reasoning line is. Before epilepsy was understood, it was believed that epilepsy attacks were caused by "diabolic possession". It's easy to imagine a debate between a skeptic and a believer in those times:

Skeptic: "I don't believe in diabolic possession, there's no evidence for that. Furthermore, there's no evidence of the existence of the demon"
Believer: "Well, if you don't believe, then ... prove that epilepsy attacks are NOT caused by diabolic possession""

We now know with great certainty what causes epilepsy, and effective cures and treatments have been developed. It is certainly not caused by "diabolic possession".

When there is no explanation for a given phenomenon, the only thing we can say for sure, and the most sensible one, is … "we still don't know"

False Dilemma

It happens when only two options of explanation of a given phenomenon are presented, when in reality there are more.

Examples:

"People are either good or evil"
"If you don't pray before having dinner, you are an atheist"
"I saw you stepping into a church the other day, so it's not true that you don't believe in God"

False Analogy

Happens when the elements used to make the analogy are not comparable in importance, significance or scope.

Example:

"If you accept that a certificate signed by the dealer is proof that George purchased that bicycle, then you must accept that a certificate signed by a UFO witness is proof that alien ships are visiting the earth"

Argument from Authority

Also known as "Argumentum ad Verecundiam". The fallacy consists in assuming that something is true because a know authority says it's true. It can be a political authority, a religious authority, a science-related authority, etc.

In some cases however, the sole word of an authority may indeed be taken seriously, especially when he/she is acknowledged by the majority of his/her peers as qualified in the field in question. But in the end, only the arguments are what count. Even authorities can make mistakes. Let's not forget that authorities such as Isaac Newton and Albert Einstein made gross mistakes in their lives, the former with the alchemy thing and the latter with the static universe assumption (among other possible ones).

The fallacy is especially valid when the authority is not qualified on the subject in discussion, or when he/she is not accepted by his/her peers. In the field of science we frequently come across this fallacy. There are scientists with a high degree of formal education whose theories are not accepted by his/her peers. They consistently refuse to show the data that supposedly back their wild claims, and yet, many people take their word and their academic position as proof that the claim is true. How many times have we heard: "telekinesis is real, I saw a PhD in physics saying so on TV the other day"

There is a famous and revealing example of this fallacy in the United States. When Jimmy Carter was still not president, he saw some lights in the sky and announced that he had seen UFOs. Later on he became a world wide authority when he became president of the most powerful nation of the world. This sole fact, plus the recognition that Carter is a man of a sturdy moral constitution and sober intellect, was enough for the UFO fans to take his word as a compelling proof that we are being visited by extraterrestrial ships. But why his presidential status, political qualifications and honesty should make him an expert in identifying lights in the sky?

Inconsistency

This fallacy takes place when an assertion is backed by mutually contradictory premises.

The UFO proponents often fall in this fallacy, when they claim that alien ships are of a so advanced technology that they are invisible to radars. But at the same time they assert that radar detection is proof of UFO visitation.

Another example of inconsistency is the claim that ghosts are invisible to the human eye, but that they can be captured by optical photographic cameras.

Attacking the Person

Better known as "Argumentum ad Hominem". It happens when a position is defended attacking personal traits of the opponent, rather than listening and analyzing his/her arguments.

Examples:

"You are not qualified to debate me on this matter because you are a boy, you are just 20"
"I have caught you lying in the past, so your points of view in any matter can't be taken seriously"

Slippery Slope

Consists in declaring unacceptable a proposition asserting that inevitable (and often nasty) consequences will follow if it is accepted, without sufficient argumentation of the said inevitability.

Examples:

"If we legalize divorce, then the fundamental unit of society, that is family, will fall apart, chaos and anarchy will reign over the countries, and civilizations will come to an end."
"If we legalize pornography, it will be a boost to immorality, and people will end up walking naked on the streets doing all kinds of obscenities"

Circular Reasoning

Also known as "Petitio Principii" or "Begging the Question". It takes place when an assertion backs itself. It's tantamount to claiming that something is true because it is true.

Although when presented this way, the fallacy is obvious, the circle of assertions that back one another can be big enough to confound the interlocutor.

Examples:

"Haunted houses are real, I heard a testimony on TV. The guy's version is trusty because he has a brother who lives in a haunted house, and why someone would lie to his brother?"
"The bible is proof that God exists, and the bible must be taken seriously because it was inspired by God"

Enumeration of Favorable Circumstances

It's a misuse of statistics to back a claim. It happens when only the cases that back the claim are considered to the statistics, and the ones that disprove it are rejected or forgotten.

This fallacy is often committed by the proponents of the premonitory dreams. It's also common on the "Cold Reading" technique. The "misses" vastly outnumber the "hits", but the person who is "read" is so emotionally committed that he/she will remember only the hits (which often are not such, but just approximations), will forget the misses altogether, and will end up believing that the reader is a real psychic.

Appeal to Popularity

Also known as "Argumentum ad Populum". It takes place when an idea or claim is accepted as true, because a lot of people think that is true.

Once again, history shows us how fallacious this idea is. There was a time when a lot of people believed that the earth was flat, that humans could not survive at speeds greater than 40 km/h, that the earth was at the center of the universe, etc. Many other beliefs that once enjoyed great popularity have been proved wrong.

Two Wrongs Make a Right

Also know as "Tu Quoque" or "You Too" . It happens when someone defends his/her position alleging that the opponent makes the same mistake he/she denounces.

Example:

Person A: "You are aggressive and arrogant, you are always attacking other people"
Person B: "And so what?,... I've heard you being aggressive to others as well"

It's clear that the fact that A is also aggressive, does not deny the fact that B is aggressive him/herself. The only thing that B can argue with certainty is that A lacks the moral authority to accuse him/her.

Confusing Cause and Effect

Also known as "Post Hoc". The fallacy consists in assuming that because phenomenon A happens after phenomenon B, then A is a consequence of B.

This reasoning is fallacious, unless the relation cause-effect has already been well studied, documented and understood.

Example:

""The earthquake hit the city just the day after we got the record high temperature in 10 years, therefore heat must be an important earthquake triggering factor.""

This is also a common fallacy in the alternative medicine field. A person who undergoes an alternative treatment and subsequently his/her health improves, will surely think that it was due to that particular treatment. But if the said treatment has not been properly documented by double blind studies, the health improvement could be explained by other reasons, such as the placebo effect.

Straw Man

I would also call it "Missing the Point". It takes place when, be it on purpose or inadvertently, a person attacks a different argument than the one his/her opponent presents. The original argument is distorted, exaggerated or simplified and is replaced by a different one, often weaker and easier to debate.

Many people use this "technique" on purpose to confound his/her opponent and to make him/her look silly or in fault.

Examples:

"Evolutionists say that life on Earth arose by random chances. Ridicule,… how a human being or an elephant could arise that way?"
"Skeptics oppose the idea that research on the paranormal is government funded. Those people are irresponsible, they pretend to render us defenceless before the threat that those phenomena pose."

Burden of Proof

This fallacy is related to the "Argument from Ignorance" fallacy. It takes place when someone makes a claim from ignorance, and then urges his/her opponent to explain it.

Example:

""The object I saw in the sky was not a plane, nor a globe, nor an helicopter, therefore it should have been an alien ship. If you don't believe me, then,… explain me what it was!""

This reasoning is erroneous, because the person who makes the claim is the one who must provide the evidence in his/her favor. The person who doubts it has no obligation to explain anything, and furthermore, is unable to give any explanation since he/she did not witness the phenomenon.

Affirming the Consequent

Any argument of the following form is decidedly wrong:

If P is true, then Q is true
Q is true
Therefore P is true

Example:

"If we contaminate the river, then an increase in fish mortality will follow. And an increase in fish mortality has been reported, so we are indeed contaminating the river"

Denying the Antecedent

Any argument of the following form is decidely wrong as well:

If P is true, then Q is true
P is not true
Therefore Q is not true

Despite the fact that this argument is erroneous at any price, many people fall in it and doesn't seem to notice.

Example:

"People who participate of skeptical organizations are reasonable and sensible, therefore everyone who doesn't participate of such organizations is a stupid"

Final commentary

The Logical Fallacies subject is much broader and more detailed than what I've mentioned here. I have examined, in a very succint manner, just those that have a more direct relation with skepticism about the paranormal, occult and supernatural (and surely enough, many of them have been left out).

But the ability to see the difference between a good and sound argument, and a poor and flawed one, is important in every aspect of human life. To accomplish this goal, we need practice, plus an open, logic and skeptic mind.

Credulity and lack of logical rigor may become dangerous enemies of people in particular, and societies in general. Many people have paid, and continues to pay, high prices for their surrender to irrationality. It often has nasty consequences. Prevention lies in reason, logic and skepticism.