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Informal Fallacies - Avoiding Common Errors in Reasoning

Informal Fallacies

The interpretation of a Biblical text is only as good as the underlying logic that supports it. God made man in His image (tzelem) and likeness (demut), and therefore made him with rationality and the ability to correctly reason about things. The Lord Jesus the Messiah is described as the "Logos" or "logic" of God, and we are called to follow Him as His talmidim (students or disciples). You simply cannot properly begin to properly read the various texts of Scripture without first being grounded in the basics of clear thinking.

This section lists some common errors in thinking that afflict all of us since the fall of Adam in Gan Eden. By familiarizing yourself with these forms of reasoning you may guard yourself from making the same sorts of errors (as well as to catch errors in the thinking of others who purport to be speaking the truth).

For a brief introduction of the subject, click here.


Fallacies of Presumption
These arguments illicitly assume the truth of their conclusion:

  1. Appeal to Ignorance: (ad Ignorantiam)
    Because something is not known to be true, it is assumed to be false (or conversely).
  2. Begging the Question: (Petitio Principii)
    The truth of the conclusion is already assumed in the premises.
  3. Complex Question:
    Two unrelated points are conjoined as a single proposition.
  4. False Dilemma:
    Two choices are given when in fact there are three (or more) options.
  5. 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.
  6. Pseudo-Tolerance:
    The assumption that "I must respect all opinions" (or some variation) ends the need for further consideration of an issue.
  7. Relativist Fallacy:
    A person rejects a claim by asserting that the claim might be true for others but is not for him/her.
  8. 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.

Non Sequiturs

The term non sequitur literally means "it does not follow." In this section we describe fallacies which occur as a consequence of invalid arguments:

  1. Affirming the Consequent:
    Any argument of the form: If p then q, q, therefore p.
  2. Denying the Antecedent:
    Any argument of the form: If p then q, not p, therefore, not q.
  3. Inconsistency:
    Asserting that contrary or contradictory statements are both true.
  4. 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.

  1. 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)
  2. 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)
  3. Style Over Substance:
    The manner in which an argument (or arguer) is presented is felt to affect the truth of the conclusion.
  4. Red Herring:
    An irrelevant topic is presented in order to divert attention from the original issue.
  5. 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.
  6. Poisoning the Wells:
    Trying to discredit what a person might later claim by presenting unfavorable information.
  7. 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.

  1. Appeal to belief:
    The fact that many people believe a claim does not, in general, serve as evidence that the claim is true.
  2. Appeal to Common Practice:
    The fact that most people do X is used as "evidence" to support the action or practice.
  3. Appeal to (fearful) Consequences:
    You are warned of unacceptable consequences.
  4. Appeal to Emotion:
    The substitution of various means of producing strong emotions in place of evidence for a claim.
  5. Appeal to Flattery:
    Flattery is used in the place of evidence for accepting a claim.
  6. Appeal to Force:
    Creating fear in people does not constitute evidence for a claim.
  7. Appeal to Novelty:
    It is assumed that something is better or correct simply because it is new.
  8. Appeal to Popularity: (ad Populum)
    A proposition is argued to be true because it is widely held to be true.
  9. Appeal to Pity: (ad Misericordiam)
    You are persuaded to agree by sympathy.
  10. Appeal to Ridicule:
    Mocking a claim does not show that it is false.
  11. Appeal to Tradition:
    It is assumed that something is better or correct simply because it is older, traditional, or "always has been done."
  12. Bandwagon:
    Peer pressure and threat of rejection do not constitute evidence for accepting or rejecting a claim.
  13. Guilt by Association:
    A person rejects a claim because it is pointed out that people she dislikes accept the claim.
  14. Prejudicial Language:
    Value or moral goodness is attached to believing the author.

Inductive Fallacies

Inductive reasoning consists of inferring from the properties of a sample to the properties of a population as a whole.

  1. Accident:
    A generalization is applied when circumstances suggest that there should be an exception.
  2. Hasty Generalization: (converse accident)
    The sample is too small to support an inductive generalization about a population
  3. Unrepresentative Sample:
    A conclusion is drawn about a population based on a sample that is biased or prejudiced in some manner.
  4. False Analogy:
    Two objects or events being compared are relevantly dissimilar.
  5. Slothful Induction:
    The conclusion of a strong inductive argument is denied despite the evidence to the contrary.
  6. Fallacy of Exclusion:
    Evidence which would change the outcome of an inductive argument is excluded from consideration.
  7. Special Pleading:
    Claiming to be exempt from certain principles or standards without providing good reasons for the exemption.
  8. Spotlight:
    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.
  9. 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.
  10. Misleading Vividness:
    A very small number of particularly dramatic events are taken to outweigh a significant amount of statistical evidence.

Causal Fallacies

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.

  1. Post Hoc:
    Because one thing follows another, it is held to cause the other.
  2. Questionable Cause:
    One event is claimed to cause another just because the events occur together.
  3. Insignificant:
    One thing is held to cause another, and it does, but it is insignificant compared to other causes of the effect.
  4. Wrong Direction:
    The direction between cause and effect is reversed.
  5. Complex Cause:
    The cause identified is only a part of a number of causes of the effect.
  6. Slippery Slope:
    A series of increasingly unacceptable consequences is drawn.

False Analogies

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:

  1. Composition:
    Because the attributes of the parts of a whole have a certain property, it is argued that the whole has that property.
  2. Division:
    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.

  1. Too Broad:
    The definition includes items which should not be included.
  2. Too Narrow:
    The definition does not include all the items which should be included.
  3. Failure to Elucidate:
    The definition is more difficult to understand than the word or concept being defined.
  4. Circular Definition:
    The definition includes the term being defined as a part of the definition.
  5. 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:

  1. Equivocation:
    The same term is used with two different meanings.
  2. Amphiboly:
    The structure of a sentence allows two different interpretations.
  3. Accent:
    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?"

  1. Subverted Support:
    The phenomenon being explained doesn't exist.
  2. Non-support:
    Evidence for the phenomenon being explained is biased.
  3. Untestability:
    The theory which explains cannot be tested.
  4. Limited Scope:
    The theory which explains can only explain one thing.
  5. Limited Depth:
    The theory which explains does not appeal to underlying causes.

Syllogistic Fallacies

These fallacies pertain to categorical statements based on traditional (Aritotelian) logic.

  1. Fallacy of Four Terms:
    A syllogism has four terms
  2. Undistributed Middle:
    Two separate categories are said to be connected because they share a common property
  3. 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
  4. 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
  5. Fallacy of Exclusive Premises:
    A syllogism has two negative premises
  6. Fallacy of Drawing an Affirmative Conclusion From a Negative Premise:
    As the name implies
  7. Existential Fallacy:
    A particular conclusion is drawn from universal premises.


I relied on the following sources to confirm my work for this portion of the Hebrew for Christians web site:

Barker, Stephen F., The Elements of Logic. Fifth Edition.McGraw-Hill, 1989

Copi, Irving M. and Cohen, Carl. Introduction to Logic. Eighth Edition. Macmillan, 1990

Purtill, Richard L., Logic for Philosophers. Harper and Row, 1971

Hurley, Patrick, A Concise Introduction to Logic, 7th ed. (Wadsworth, 2000). [My personal favorite for a good overview of the subject.]

Engel, S. Morris, With Good Reason: An Introduction to Informal Fallacies (St. Martin's, 1994)

Stephen's Guide to the Logical Fallacies

Dr. Michael C. Labossiere, the author of a Macintosh tutorial called Fallacy Tutorial Pro 3.0, has graciously agreed to let me use portions of his work to appear on this site. Portions remain © Copyright 1995 Michael C. Labossiere. Dr. Labossiere may be reached at

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