Logical Fallacies

False Equivalence

2012-12-18T12:32:46.221-08:00

Description

False equivalence is a logical fallacy where there appears to be a logical equivalence between two opposing arguments, but when in fact there is none. Journalists use a form of this logical fallacy when comparing two sides of a scientific debate in an attempt to provide a balance between a scientific and denialist point of view. However, there is no equivalence between the two sides, when one is supported by evidence, and the other side with little or no evidence, of which most is of low quality. In other words, in false equivalence, someone will state that the opposing arguments have a passing similarity in support, when, on close examination, there is large difference between the quality of evidence

Example

Marijuana and alcohol are both drugs. An ounce is about the same as three bottles. If you think one should be legal, you should think the same of the other.

Post hoc ergo propter hoc

2012-10-05T12:12:42.766-07:00

Description

Also known as the post hoc, Post hoc ergo propter hoc is a Latin phrase, literally translated as "after this, therefore because of this." It is a fallacious argument that states that because a second event follows the first, the first event must be the cause of the second. Many superstitions are based on this type of argument, because the observer may notice that performing one action seems to lead to another.

Although post hoc observations may lead to a testable hypothesis, there must be evidence of a mechanism that extends the correlation to causation.

Example

My child broke her leg after she was vaccinated, so vaccines cause broken legs.

Cherry Picking or Quote Mining

2012-09-19T22:55:31.428-07:00

Description

Cherry picking is a fallacy where only select evidence is presented in order to persuade the audience to accept a position, and evidence that would go against the position is withheld. The stronger the the withheld evidence, the more fallacious the argument. Quote mining is a form of cherry picking, and the genuine points used in construction of straw man arguments are typically cherry-picked.

Example

You should be a Christian, because God is all about love and forgiveness, and those are great things.

Nirvana Fallacy

2012-09-07T10:27:00.827-07:00

Description

The Nirvana Fallacy is an attempt to compare a realistic solution with an idealized one, and dismissing or even discounting the realistic solution as a result of comparing to a “perfect world” or impossible standard. This reasoning ignores the fact that improvements are often good enough.

Example

What’s the point of making drinking illegal under the age of 21? Kids still manage to get alcohol.

Poisoning the Well

2012-06-04T11:22:35.901-07:00

Description

To Poison the Well means to pre-provide any information that could produce a biased opinion of the reasoning, positive or negative. It is related to the ad hominem argument.

Example

Remember, Big Pharma supports vaccines, so any research that supports vaccines should be examined carefully.

Argumentum Ad Hominem

2012-06-04T11:16:58.079-07:00

Description

The Argumentum ad hominem, or simply ad hominem argument, applies to any argument that centers on emotional (specifically irrelevant emotions) rather than rational or logical appeal. An ad hominem argument occurs when one attacks the person making an argument rather than the argument itself.

Example

You're a shill for Big Pharma so any of your statements about vaccine safety can't be trusted because Big Pharma is paying you off.

Fallacy of Division

2012-06-02T11:54:11.554-07:00

Description

The Fallacy of Division is an incorrect inference that the qualities of the parts can be deduced from the characteristics of the whole. It is the opposite of the Fallacy of Composition.

Example

Humans are visible to the naked eye.
Humans are made up of human cells.
Therefore, human cells are visible to the naked eye.

Fundamental Attribution Error (or Correspondence Bias)

2012-06-02T09:48:32.040-07:00

Description

The fundamental attribution error (also known as correspondence bias or attribution effect) describes the tendency to over-value dispositional or personality-based explanations for the observed behaviors of others while under-valuing situational explanations for those behaviors. The fundamental attribution error is most visible when people explain the behavior of others. It does not explain interpretations of one's own behavior—where situational factors are often taken into consideration. Fundamental attribution error is a social/psychological bias, is not a true logical fallacy. However, it is frequently used in arguments or debates.

Example

As a simple example, if Alice saw Bob trip over a rock and fall, Alice might consider Bob to be clumsy or careless (dispositional). If Alice tripped over the same rock herself, she would be more likely to blame the placement of the rock (situational).

Special Pleading

2012-05-21T23:05:23.948-07:00

Description

Special pleading is a form of spurious argumentation where a position in a dispute introduces favorable details or excludes unfavorable details by alleging a need to apply special considerations or exemptions from typical analysis. These considerations or exemptions are pushed into the argument without proper criticism. Essentially, this involves someone attempting to cite something as an exemption to a generally accepted rule, principle, etc. without justifying the exemption.

This fallacious argument is one of the most used in alternative medicine and other pseudoscientific areas, since, lacking any scientific evidence, they attempt to excuse the lack of evidence not because of implausibility, but because we lack the abilities to understand their special mechanism. Often, you will here the phrase, "mainstream science just hasn't uncovered the mechanism yet."

Example

Homeopathy cannot be tested with modern science because we do not have a proper understanding of its mechanisms.

False Dichotomy

2012-04-19T10:57:03.147-07:00

Description

A False Dichotomy, or false dilemma, is a dichotomy (a set of two mutually exclusive, jointly exhaustive alternatives) of arguments that ignores the potential for an infinite set of alternative arguments; for an infinite number of overlapping arguments; or for the potential that neither part of the dichotomy is correct. A false dichotomy is often employed by an arguer to force the other side into an extreme position by assuming that there are only two possible positions. At it's essence, it says "you are either with us or against us," which ignores the all other possibilities, such as "we are with you on points A&B, but against you on points C,D&E."

Example

Because evolution has not been unable to show exactly how life arose, evolution is therefore disproved, and creationism is obviously the correct answer.

Confirmation Bias

2012-04-05T12:23:07.730-07:00

Description

Confirmation Bias is simply the tendency for individuals to favor information or data that support their beliefs. It is the tendency for people to only seek out information that conforms to their pre-existing view points, and subsequently ignore information that goes against them. It is a type of cognitive bias and a form of selection bias toward confirmation of the hypothesis under study. Avoiding confirmation bias is an important part of rationalism and in science in general. This is achieved by setting up problems so that you must find ways of disproving your hypothesis (see falsifiability).

Example

Psychic "readings" is that listeners apply a confirmation bias which fits the psychic's statements to their own lives. By making a large number of ambiguous statements in each sitting, the psychic gives the client more opportunities to find a match. This is one of the techniques of cold reading, with which a psychic can deliver a subjectively impressive reading without any prior information about the client.

Fallacy of Composition

2012-03-19T14:53:40.541-07:00

Description

The Fallacy of Composition is an incorrect inference that the qualities of the whole can be made from the qualities of one of its parts. It is the opposite of the Fallacy of Division.

Example

Human cells are invisible to the naked eye.
Humans are made up of human cells.
Therefore, humans are invisible to the naked eye.

Argument from Ignorance

2012-03-19T14:25:24.299-07:00

Description

Argument from ignorance infers that a proposition is true from the fact that it is not proven to be false (or alternatively, that a proposition is false because it is not proven to be true). The old argument that "the absence of evidence is not evidence of absence" is a form of this logical fallacy, because absence of evidence can be evidence of absence if substantial attempts to find evidence have proven negative. The fallacy also asserts that a proposition is true because it has not yet been proven false, or it is "generally accepted" (or vice versa).

Furthermore, this argument presumes that there are only two choices: true or false. In fact, there are other choices, including "not enough investigation has been completed to choose between true or false." So a non-fallacious argument may be made that a proposition is not false because insufficient testing has been done to show it false. That is a reasonable argument.

Appeals to ignorance are used to shift the burden of proof to the other side. However, the burden of proof should be on the side that is making the assertion, not on the side that disputes the assertion.

Example

There is no evidence that says a god doesn't exist, so a god must exist.

Non Sequitur

2012-03-13T15:22:09.528-07:00

Description

Non Sequitur is the Latin phrase for "(it) does not follow."It means that the conclusion reached does not follow from the premise(s). Examples of ''non sequitur'' arguments are hilariously disconnected, but often they can be subtle and may not be easily uncovered. The arguments are fallacious since they do not provide any evidence for an argument and are just meant to confuse the listener.

Example

Homeopathy comes in pretty bottles. Therefore, homeopathy can cure cancer.

Strawman Argument

2012-03-09T17:32:29.019-08:00

Description

A Strawman Argument, or simply strawman, is an argument that misrepresents a position of the other side, in order to make it appear weaker than it actually is. The arguer then refutes the arguer's misrepresentation of the position, leading others to conclude that the real position has been refuted.

It is an intentional misrepresentation of an opponent's position, often used in debates with unsophisticated audiences to make it appear that the opponent's arguments are more easily defeated than they are. This is a fallacy, of course, because it has done nothing to actually refute the position of the other side of the argument, nor provide any evidentiary support of either side of the argument.

Example

The pro-vaccination doctors do not care about our autistic children, so vaccines are bad.

Appeal to Nature

2012-03-06T13:02:30.019-08:00

Description

Appeal to Nature, similar to the naturalistic fallacy, when used as a fallacy, is the belief or suggestion that “natural” is always better than “unnatural”. It assumes that "nature" is good, and "unnatural" is not. Unfortunately, in many discussions about science and medicine, individuals take this as their default belief.

Example

High fructose corn syrup is not natural so it must be bad for you.

Naturalistic Fallacy

2012-03-06T13:02:29.465-08:00

Description

The Naturalistic Fallacy is similar to the appeal to nature, where the conclusion expresses what ought to be, based only on actually what is more natural. This is very common and most people never see the problem with these kind of assertions due to accepted social and moral norms. This bypasses reason and we fail to ask why something that is, ought to be that way.

Example

Homosexuality is morally wrong because in nature, sex is used for reproduction.

Appeal to Novelty

2012-03-06T13:02:28.485-08:00

Description

Appeal to Novelty, the opposite of the Appeal to Antiquity, is an argument that the novelty or newness of an idea is itself evidence of its truth. Since every rejected idea in the history of man was once a "novel idea", the fallaciousness of this argument is apparent.

Example

If you want to lose weight, your best bet is to follow the latest diet..

Appeal to Consequences

2012-03-06T13:02:27.992-08:00

Description

Appeal to consequences is an attempt to motivate belief with an appeal either to the good consequences of believing or the bad consequences of disbelieving, without respect to the quality of the evidence supporting such an argument. Of course, there may be consequences to a belief, as long as it is supported by evidence.

Example

Belief in evolution will lead to mass genocide.

Appeal to Authority

2012-03-06T13:02:27.562-08:00

Description

Appeal to authority is a logical fallacy which provides an argument from an authority, but on a topic outside of the authority's expertise or on a topic on which the authority is not disinterested (i.e., is biased). Almost any subject has an authority on every side of the argument, even where there is generally agreed to be no argument. When correctly applied, it can be a valid and sometimes essential part of an argument that requests judgement or input from a qualified or expert source.

Example

Dr. Smith, an expert in computer engineering, does not believe in climate change, so obviously climate change is false.

Appeal to Antiquity or Tradition

2012-03-06T13:02:27.086-08:00

Description

Appeal to antiquity is a common logical fallacy that occurs when it is assumed that something is better or correct simply because it is older, traditional, or “always has been done.”

Example

Homeopathy has been around 200 years, so obviously it must work.

Genetic Fallacy

2012-03-06T13:02:26.294-08:00

Description

This Genetic Fallacy creates an argument that is accepted or rejected based on the source of the evidence, rather than on the quality or applicability of the evidence. It is also a line of reasoning in which a perceived defect in the origin of a claim or thing is taken to be evidence that discredits the claim or thing itself.

Example

He has a medical degree and doesn't like vaccines, so obviously vaccines are bad.

Slippery Slope Fallacy

2012-03-05T22:41:59.644-08:00

Description

Slippery Slope Fallacies are arguments that utilize the false assumption that once a first step is taken, it predicts the next step, which then leads to the next step until some conclusion is reached that supports the initial idea. The arguer then concludes that we therefore shouldn’t do the first thing. There are several issues with this type of fallacy, specifically, it makes a prediction that simply cannot be proven. It also assumes that there isn't a restraint placed on subsequent steps that modify the conclusion.

Example

If you teach evolution in school, you start down the slippery slope to immorality.

Gambler's Fallacy

2012-03-05T22:41:59.024-08:00

Description

The Gambler’s Fallacy is the fallacy of assuming that a short-term deviation from statistical probability will be corrected in the short-term. In a totally random event, past performance has no effect on the next attempt. Arguing that a totally random event may have a result that will self-correct the "average" is fallacious. is the false belief that a random process becomes less random, and more predictable, as it is repeated. This is most commonly seen in gambling, hence the name of the fallacy. For example, a person playing craps may feel that the dice are "due" for a certain number, based on their failure to win after multiple rolls. This is a false belief as the odds of rolling a certain number are the same for each roll, independent of previous or future rolls.

Example

This coin has landed heads-up nine times in a row. Therefore,
It will probably land tails-up next time it is tossed.

This inference is an example of the gambler’s fallacy. When a fair coin is tossed, the probability of it landing heads-up is 50%, and the probability of it landing tails-up is 50%. These probabilities are unaffected by the results of previous tosses.The gambler’s fallacy appears to be a reasonable way of thinking because we know that a coin tossed ten times is very unlikely to land heads-up every time. If we observe a tossed coin landing heads-up nine times in a row we therefore infer that the unlikely sequence will not be continued, that next time the coin will land tails-up. In fact, though, the probability of the coin landing heads-up on the tenth toss is exactly the same as it was on the first toss. Past results don’t bear on what will happen next.

Argument from Fallacy

2012-03-05T22:41:58.282-08:00

Description

The Fallacist’s Fallacy, also known as argument to logic (argumentum ad logicam), fallacy fallacy, or fallacist's fallacy, is dismissing a proposition because on of its supporting arguments contains a logical fallacy. In other words, the rejection of an idea as false simply because the argument used to support the idea is itself fallacious. Just because one argument lacks merit or is fallacious, that it is not sufficient evidence to reject the idea.

Example

Tom: OK — I'll prove I'm English — I speak English so that proves it.
Bill: But Americans and Canadians, among others, speak English too. You are assuming that speaking English and being English always go together. That means you are not English..

Bandwagon Fallacy

2012-03-05T22:24:53.071-08:00

Description

The Bandwagon Fallacy is committed by an argument that appeals to the growing popularity of an idea. This popularity is used as the reason for accepting it as true.

Such an argument is fallacious because popularity may not arise from an actual fact, but may result from peer pressure, political expediency, or even plain mass stupidity. Popularity does not guarantee the truthfulness of an argument.

Example

Creationism is supported by most Americans, so it must be true.