Logic and Fallacies Exam 2

Basic framework of a deductive argument

P1: If A, B, and C are satisfied, then Q. P2: A, B, and C are satisfied. C: Therefore, Q.

Formal fallacy

A fallacy detectable by analyzing the logical form of an argument.

Informal fallacy

A fallacy detectable by examining the content or context of an argument.

Can deductive and non-deductive arguments contain fallacies?

Yes, both types of arguments can contain fallacies.

Modus ponens

P → Q; P; therefore Q. A valid deductive form.

Affirming the consequent

P → Q; Q; therefore P. Invalid because Q could have another cause.

Denying the antecedent

P → Q; ¬P; therefore ¬Q. Invalid because Q could still be true.

How do you expose a formal fallacy?

Give a counterexample showing the premises can be true while the conclusion is false.

Three categories of informal fallacies

Relevance; weak induction; presumption, ambiguity, and illicit transference.

Fallacy of relevance

Premises are logically irrelevant to the conclusion.

How do you identify a fallacy of relevance?

Cross out irrelevant claims and examine what support for the conclusion remains.

Appeal to force

Threatening harm or negative consequences unless the audience accepts a conclusion.

Appeal to pity

Trying to gain acceptance of a conclusion by eliciting pity.

Appeal to the people

Seeking agreement by appealing to crowd emotions, belonging, or desires for superiority.

Bandwagon fallacy

Claiming something is true or right because many people believe or do it.

Appeal to vanity or snobbery

Suggesting someone should agree to feel special, superior, or socially desirable.

Appeal to tradition

Claiming something should be accepted because it is traditional.

Argument against the person (ad hominem)

Attacking an opponent instead of addressing their actual argument.

Abusive ad hominem

Using insults or verbal abuse against the person making an argument.

Circumstantial ad hominem

Dismissing an argument by attacking the speaker's motives or circumstances.

Tu quoque (you too)

Calling someone hypocritical instead of addressing whether their argument is true.

When are personal flaws relevant to an argument?

When they directly affect the issue, such as a witness's reliability or a candidate's honesty.

Fallacy of accident

Applying a general rule to a specific case the rule was not intended to cover.

Straw man fallacy

Misrepresenting an opponent's argument and then attacking the distorted version.

How do you expose a straw man?

Show how the original argument was misrepresented or an important qualification was omitted.

Red herring

Introducing an irrelevant issue that distracts from the original argument.

Weak induction fallacy

Premises are relevant but provide insufficient support for the conclusion.

Appeal to unqualified authority

Relying on an authority who lacks relevant expertise, is unreliable, or is biased.

When is an appeal to authority stronger?

When the authority has relevant expertise, credibility, and appropriate independence.

Appeal to ignorance

Claiming something is true because it has not been proven false, or false because it has not been proven true.

Principle behind appeal to ignorance

Absence of evidence is not automatically evidence of absence.

Appeal to ignorance: courtroom exception

If guilt is not proven beyond a reasonable doubt, the defendant is treated as not guilty.

When can absence of evidence be meaningful?

When a thorough, reliable search would likely have detected the evidence if it existed.

Hasty generalization

Drawing a broad conclusion from a sample that is too small, atypical, or not randomly selected.

Converse accident

Drawing an overly broad generalization from particular cases; reasoning from particular cases to a general rule.

False cause

Mistaking a relationship or sequence of events for a genuine causal relationship.

Post hoc fallacy

Assuming that because B followed A, A caused B.

Non causa pro causa

Treating something that is not the actual cause as if it were the cause.

Oversimplified cause

Treating a partial cause as the sole or complete explanation of an outcome.

Gambler's fallacy

Assuming independent chance events influence each other's likelihood based on previous outcomes.

Slippery slope

Arguing that one step will trigger a chain of events leading to disaster without adequate support.

How do you evaluate a slippery slope?

Examine each causal link and identify the weakest or least-supported step.

Weak analogy

Drawing a conclusion from a comparison between things that are not sufficiently similar in relevant ways.

What determines the strength of an analogy?

The strength and relevance of similarities to the conclusion.

Four explanations for correlation

Causation; reverse causation; common cause; mere coincidence.

Strength of a non-deductive argument

How much support its premises provide for its conclusion.

Cogent argument

A strong non-deductive argument with true premises.

Logical contradiction

P ∧ ¬P: asserting both a proposition and its negation.

Law of non-contradiction

¬(P ∧ ¬P): a proposition and its negation cannot both be true in the same respect and at the same time.

Contradiction in terms

A phrase whose words conflict in meaning, such as "square circle."

Proof by contradiction (reductio ad absurdum)

Assume a position and derive a contradiction or absurd consequence to argue against it.

Self-sealing position

A position that resists refutation by dismissing or redefining any counterevidence.

Fallacy of presumption

An argument that relies on an unjustified assumption or takes something for granted.

Begging the question

Assuming the conclusion is true in the premises instead of independently supporting it.

Direct circular reasoning

The conclusion is explicitly restated as a premise.

Indirect circular reasoning

The conclusion is supported by a premise that depends on the conclusion being true.

Shaky implicit premise

An unstated assumption that is questionable or lacks adequate support.

Complex question fallacy

Asking a question that presupposes an unproven claim, often trapping the respondent.

False dichotomy

Presenting only two options when additional reasonable possibilities exist.

Suppressed evidence

Ignoring or omitting important evidence that would weaken the argument or change the conclusion.

Fallacy of ambiguity

A fallacy that relies on unclear or shifting meanings in words or sentence structure.

Equivocation

Using a word in different senses within the same argument.

Amphiboly

Ambiguity caused by the grammatical structure of a sentence.

How do you respond to equivocation or amphiboly?

Clarify the possible meanings and show whether the argument fails under the intended interpretation.

Homophone

A word that sounds like another word but has a different meaning; spelling may differ.

Homograph

A word with the same spelling as another word or sense but a different meaning.

Fallacy of composition

Assuming that what is true of the parts or members must be true of the whole.

Fallacy of division

Assuming that what is true of the whole must be true of each part or member.

Illicit transference

Improperly transferring a property between a whole and its parts, or vice versa.

Law of excluded middle

P ∨ ¬P: a proposition is true or false; there is no third truth value in classical logic.

Tertium non datur

"No third option is given"; refers to the law of excluded middle.

Law of excluded middle versus false dichotomy

P ∨ ¬P is a true logical dichotomy; a false dichotomy wrongly limits real-world options.

Is P ∨ Q always true?

No. A disjunction is false if both P and Q are false.

How does circular reasoning create a flawed argument?

The conclusion may follow from its premises, but the premises provide no independent support.

Deductive reasoning

Aims to establish that the conclusion follows necessarily from the premises.

Non-deductive reasoning

Provides probabilistic or defeasible support rather than guaranteeing the conclusion.

Argument reconstruction

Clarifying an argument by identifying its premises, conclusion, and underlying reasoning.

Three signs of suspicious or immoral practices

Reasoned arguments against the practice; defenses based on tradition, necessity, or human nature; strategic ignorance.

Strategic ignorance

Deliberately turning attention away from the immoral or troubling aspects of a practice.

Dilemma in logic

An argument using alternatives to support a conclusion; assess whether the alternatives are exhaustive and the reasoning is valid.

How do you test an alleged fallacy?

Identify its structure or assumptions, explain the error, and use a counterexample when appropriate.

Appeal to force versus appeal to pity

Force uses threats; pity uses sympathy or compassion.

Straw man versus red herring

Straw man distorts an opponent's argument; red herring distracts with an irrelevant issue.

Accident versus converse accident

Accident applies a general rule to an exceptional case; converse accident generalizes from particular cases.

Composition versus division

Composition transfers properties from parts to whole; division transfers properties from whole to parts.

Equivocation versus amphiboly

Equivocation involves a word's meaning; amphiboly involves grammatical sentence structure.

Appeal to the people versus appeal to authority

Appeal to the people targets crowd emotions or social desires; appeal to authority relies on an authority's testimony.

False cause versus slippery slope

False cause mistakes a causal relationship; slippery slope predicts an inadequately supported chain of consequences.

Hasty generalization versus appeal to ignorance

Hasty generalization uses an unrepresentative sample; appeal to ignorance treats lack of proof as evidence.

What does "better in absolute terms" mean?

Better by an independent standard, regardless of how others perform.

What does "worse compared to others" mean?

Lower in relative standing compared with other people or options.

What is the role of P ∨ ¬P in logic?

It expresses an exhaustive logical alternative and can support dilemmas and disjunctive syllogisms.

What is disjunctive syllogism?

P ∨ Q; ¬P; therefore Q, assuming the premises are true.

What are the three informal fallacy categories?

Relevance; weak induction; presumption, ambiguity, and illicit transference.

How can you evaluate a causal explanation?

Check for causation, reverse causation, a common cause, and mere coincidence.

What makes a generalization reliable?

A sufficiently large, representative, and appropriately selected sample.

What makes a slippery slope argument weak?

One or more causal links are unlikely or unsupported.

What is a counterexample used for?

To show that an argument's premises can be true while its conclusion is false.