A fallacy is, very generally, an error in reasoning. This differs from
a factual error, which is simply being wrong about the facts. To be
more specific, a fallacy is an "argument" in which the premises given
for the conclusion do not provide the needed degree of support. A
deductive fallacy is a deductive argument that is invalid (it is such
that it could have all true premises and still have a false
conclusion). An inductive fallacy is less formal than a deductive
fallacy. They are simply "arguments" which appear to be inductive
arguments, but the premises do not provided enough support for the
conclusion. In such cases, even if the premises were true, the
conclusion would not be more likely to be true. source
- Ad Hominem
- Ad Hominem Tu Quoque
- Appeal to Authority
- Appeal to Belief
- Appeal to Common Practice
- Appeal to Consequences of a Belief
- Appeal to Emotion
- Appeal to Fear
- Appeal to Flattery
- Appeal to Novelty
- Appeal to Pity
- Appeal to Popularity
- Appeal to Ridicule
- Appeal to Spite
- Appeal to Tradition
- Begging the Question
- Biased Sample
- Burden of Proof
- Circumstantial Ad Hominem
- Confusing Cause and Effect
- False Dilemma
- Gambler's Fallacy
- Genetic Fallacy
- Guilt By Association
- Hasty Generalization
- Ignoring A Common Cause
- Middle Ground
- Misleading Vividness
- Personal Attack
- Poisoning the Well
- Post Hoc
- Questionable Cause
- Red Herring
- Relativist Fallacy
- Slippery Slope
- Special Pleading
- Straw Man
- Two Wrongs Make A Right
Fallacies of Presumption source
These arguments illicitly assume the truth of their conclusion:
- Appeal to Ignorance: (ad Ignorantiam)
Because something is not known to be true, it is assumed to be false (or conversely).
- Begging the Question: (Petitio Principii)
The truth of the conclusion is already assumed in the premises.
- Complex Question:
Two unrelated points are conjoined as a single proposition.
- False Dilemma:
Two choices are given when in fact there are three (or more) options.
- Hegelian Fallacy
It is assumed that the middle position between two extremes must be correct simply because it is the middle position. Named after the philosopher G. W. Hegel (1770-1831), the target of Soren Kierkegaard’s ruthless (and prophetic) irony.
The assumption that "I must respect all opinions" (or some variation) ends the need for further consideration of an issue.
- Relativist Fallacy:
A person rejects a claim by asserting that the claim might be true for others but is not for him/her.
- Who is to say?
Affecting a skeptical attitude with the rhetorical “Who is to say?” question is supposed to “prove” that there is no way to decide whether any position or view is better than another. Assumes that the truth is unknowable.
The term non sequitur literally means "it does not follow." In this section we describe fallacies which occur as a consequence of invalid arguments:
- Affirming the Consequent:
Any argument of the form: If p then q, q, therefore p.
- Denying the Antecedent:
Any argument of the form: If p then q, not p, therefore, not q.
Asserting that contrary or contradictory statements are both true.
- Missing the Point (Ignoratio Elenchi)
An argument in defense of one conclusion instead proves a different conclusion.
Changing the Subject
The fallacies in this section change the subject by discussing the person making the argument instead of discussing reasons to believe or disbelieve the conclusion.
- Attacking the Person: (ad hominem)
(a) the person's character is attacked (abusive)
(b) the person's circumstances are noted (circumstantial)
(c) the person does not practice what is preached (tu quoque)
- Appeal to Authority: (ad verecundiam)
The fact that some sort of authority states something does not, in general, serve as evidence that the claim is true. This is especially true if:
(a) the authority is not an expert in the field
(b) experts in the field disagree
(c) the authority was joking, drunk, or in some other way not being serious
(d) the authority in question is not named (anonymous authority)
- Style Over Substance:
The manner in which an argument (or arguer) is presented is felt to affect the truth of the conclusion.
- Red Herring:
An irrelevant topic is presented in order to divert attention from the original issue.
- Genetic Fallacy:
A perceived defect in the origin of a claim or thing is taken to be evidence that discredits the claim or thing itself.
- Poisoning the Wells:
Trying to discredit what a person might later claim by presenting unfavorable information.
- Straw Man:
Attack an argument different from (and weaker than) the opposition's best argument.
Appeals to Ulterior Motives
The fallacies in this section have in common the practice of appealing to emotions or other psychological factors. In this way, they do not provide reasons for belief.
- Appeal to belief:
The fact that many people believe a claim does not, in general, serve as evidence that the claim is true.
- Appeal to Common Practice:
The fact that most people do X is used as "evidence" to support the action or practice.
- Appeal to (fearful) Consequences:
You are warned of unacceptable consequences.
- Appeal to Emotion:
The substitution of various means of producing strong emotions in place of evidence for a claim.
- Appeal to Flattery:
Flattery is used in the place of evidence for accepting a claim.
- Appeal to Force:
Creating fear in people does not constitute evidence for a claim.
- Appeal to Novelty:
It is assumed that something is better or correct simply because it is new.
- Appeal to Popularity: (ad Populum)
A proposition is argued to be true because it is widely held to be true.
- Appeal to Pity: (ad Misericordiam)
You are persuaded to agree by sympathy.
- Appeal to Ridicule:
Mocking a claim does not show that it is false.
- Appeal to Tradition:
It is assumed that something is better or correct simply because it is older, traditional, or "always has been done."
Peer pressure and threat of rejection do not constitute evidence for accepting or rejecting a claim.
- Guilt by Association:
A person rejects a claim because it is pointed out that people she dislikes accept the claim.
- Prejudicial Language:
Value or moral goodness is attached to believing the author.
Inductive reasoning consists of inferring from the properties of a sample to the properties of a population as a whole.
A generalization is applied when circumstances suggest that there should be an exception.
- Hasty Generalization: (converse accident)
The sample is too small to support an inductive generalization about a population
- Unrepresentative Sample:
A conclusion is drawn about a population based on a sample that is biased or prejudiced in some manner.
- False Analogy:
Two objects or events being compared are relevantly dissimilar.
- Slothful Induction:
The conclusion of a strong inductive argument is denied despite the evidence to the contrary.
- Fallacy of Exclusion:
Evidence which would change the outcome of an inductive argument is excluded from consideration.
- Special Pleading:
Claiming to be exempt from certain principles or standards without providing good reasons for the exemption.
A person uncritically assumes that all members or cases of a certain class or type are like those that receive the most attention or coverage in the media.
- The Gambler’s Fallacy:
A person assumes that a departure from what occurs on average or in the long term will be corrected in the short term.
- Misleading Vividness:
A very small number of particularly dramatic events are taken to outweigh a significant amount of statistical evidence.
It is common for arguments to conclude that one thing causes another. But the relation between cause and effect is a complex one. It is easy to make a mistake.
- Post Hoc:
Because one thing follows another, it is held to cause the other.
- Questionable Cause:
One event is claimed to cause another just because the events occur together.
One thing is held to cause another, and it does, but it is insignificant compared to other causes of the effect.
- Wrong Direction:
The direction between cause and effect is reversed.
- Complex Cause:
The cause identified is only a part of a number of causes of the effect.
- Slippery Slope:
A series of increasingly unacceptable consequences is drawn.
These fallacies occur because the author mistakenly assumes that the whole is nothing more than the sum of its parts. However, things joined together may have different properties as a whole than any of them do separately:
Because the attributes of the parts of a whole have a certain property, it is argued that the whole has that property.
Because the whole has a certain property, it is argued that the parts have that property.
Fallacies of Definition
In order to make our words or concepts clear, we use a definition. The purpose of a definition is to state exactly what a word means. A good definition should enable a reader to 'pick out' instances of the word or concept with no outside help.
- Too Broad:
The definition includes items which should not be included.
- Too Narrow:
The definition does not include all the items which shouls be included.
- Failure to Elucidate:
The definition is more difficult to understand than the word or concept being defined.
- Circular Definition:
The definition includes the term being defined as a part of the definition.
- Self-Stultifying Conditions:
The definition is self-contradictory.
Fallacies of Ambiguity
The fallacies in this section are all cases where a word or phrase is used unclearly. There are two ways in which this can occur: (1) The word or phrase may be ambiguous, in which case it has more than one distinct meaning; or (2) the word or phrase may be vague, in which case it has no distinct meaning:
The same term is used with two different meanings.
The structure of a sentence allows two different interpretations.
The emphasis on a word or phrase suggests a meaning contrary to what the sentence actually says.
Fallacies of Explanation
An explanation is a form of reasoning which attempts to answer the question "why?" For example, it is with an explanation that we answer questions such as, "Why is the sky blue?"
- Subverted Support:
The phenomenon being explained doesn't exist.
Evidence for the phenomenon being explained is biased.
The theory which explains cannot be tested.
- Limited Scope:
The theory which explains can only explain one thing.
- Limited Depth:
The theory which explains does not appeal to underlying causes.
These fallacies pertain to categorical statements based on traditional (Aritotelian) logic.
- Fallacy of Four Terms:
A syllogism has four terms
- Undistributed Middle:
Two separate categories are said to be connected because they share a common property
- Illicit Major:
The predicate of the conclusion talks about all of something, but the premises only mention some cases of the term in the predicate
- Illicit Minor:
The subject of the conclusion talks about all of something, but the premises only mention some cases of the term in the subject
- Fallacy of Exclusive Premises:
A syllogism has two negative premises
- Fallacy of Drawing an Affirmative Conclusion From a Negative Premise:
As the name implies
- Existential Fallacy:
A particular conclusion is drawn from universal premises