informal fallacies “a short catalog of informal fallacies”

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Informal Fallacies http://ww2.coastal.edu/dearl/PHIL101/Fallacies.html “A Short Catalog of Informal Fallacies” Evaluation & Critique

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Page 1: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Informal Fallacies

http://ww2.coastal.edu/dearl/PHIL101/Fallacies.html “A Short Catalog of Informal Fallacies”

Evaluation & Critique

Page 2: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Fallacies of Presumption

Where premises presume what is to be proved– Begging the Question– Complex Question– False Dichotomy (the “Either…Or…” Fallacy)– Suppressed Evidence

Page 3: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Begging the Question (BQ)

a form of illicit reasoning wherein the illusion is produced by verbal wordplay that a conclusion has been proved. – Illicit assumption– Rhetorical rephrasing– Circular Reasoning

Page 4: Informal Fallacies  “A Short Catalog of Informal Fallacies”

BQ: Circular Reasoning

occurs when the truth of the conclusion rests on premises whose own truth rests on the truth of the conclusion.

For Example:

It says in the Bible that God exists. Since the Bible is God’s word, and God never speaks falsely, then everything in the Bible must be true. So, God must exist.

Page 5: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

It says in the Bible that God exists. Since the Bible is God’s word, and God never speaks falsely, then everything in the Bible must be true. So, God must exist.

What is the conclusion of this argument?So, God must exist.

Page 6: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

It says in the Bible that God exists. Since the Bible is God’s word, and God never speaks falsely, then everything in the Bible must be true. So, God must exist.

What are the premises?(1) It says in the Bible that God exists.(2) The Bible is God’s word.(3) God never speaks falsely.(4) Everything in the Bible must be true.

Page 7: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

The conclusion is:So, God must exist.

What is the offending premise, i.e., the premise or premises that presumes this conclusion?:(1) It says in the Bible that God exists.(2) The Bible is God’s word.(3) God never speaks falsely.(4) Everything in the Bible must be true.

Page 8: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

The conclusion is:So, God must exist.

The offending premise is:(3) God never speaks falsely

and to a lesser extent

(2) The Bible is God’s word.

In other words, the premises assert that God exists and speaks – but not falsely, and the Bible is a record of this.

Page 9: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

BQ: Circular Reasoning

Definition: occurs when the truth of the conclusion rests on premises whose own truth rests on the truth of the conclusion.

Explanation: Only existing beings can speak. If God speaks - as it says in a premise, then God is thereby presumed to exist. So the conclusion that “God must exist” rests on a premise which already implicitly asserts his existence.

Page 10: Informal Fallacies  “A Short Catalog of Informal Fallacies”

BQ: Illicit Assumption

occurs when a key premise is left unsaid, a premise whose truth is dubitable or controversial.

For Example:

Murder is morally wrong. Therefore, abortion is morally wrong.

Page 11: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

Murder is morally wrong. Therefore, abortion is morally wrong.

What is the conclusion of this argument?Therefore, abortion is morally wrong.

Page 12: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

Murder is morally wrong. Therefore, abortion is morally wrong.

What is the premise?(1) Murder is morally wrong.

Page 13: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

The conclusion is:Therefore, abortion is morally wrong.

What is the assumption, the unstated premise, that presumes this conclusion?:(*) Abortion is murder.

Page 14: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

BQ: Illicit Assumption

Definition: occurs when a key premise is left unsaid, a premise whose truth is dubitable or controversial.

Explanation: The arguer assumes that abortion is murder. This is precisely the statement that demands proving in order to accept the main conclusion of the argument, i.e., abortion is morally wrong.

Page 15: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Complex Question

occurs when a questioner attempts to trap a respondent by asking a supposedly simple question which in fact contains two distinct questions.

For Example:

Where did you hide the drugs you stole?

Page 16: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

Where did you hide the drugs you stole?

What are the two questions (or statements) implicit in this one question?(1) Where did you hide the drugs? (or You hid

drugs.)(2) Did you steal drugs? (or You stole drugs.)

In other words, the very question presumes the drugs are stolen.

Page 17: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

BQ: Complex Question

Definition: occurs when a questioner attempts to trap a respondent by asking a supposedly simple question which in fact contains two distinct questions.

Explanation: The question is deceptively simple. It really contains two questions: (1) where are the drugs and (2) did you steal them. In fact, the question presumes the drugs are stolen.

Page 18: Informal Fallacies  “A Short Catalog of Informal Fallacies”

False Dichotomy

an illicit form of reasoning in which two alternatives (in either-or form) are presented as if their were no other alternatives when, in fact, other more palatable alternatives likely exist.

For Example:

If you don’t love America then just get the hell out.

Page 19: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

False DichotomyDefinition: an illicit form of reasoning in which two

alternatives (in either-or form) are presented as if their were no other alternatives when, in fact, other more palatable alternatives likely exist.

Explanation: ???

If you don’t love America then just get the hell out.

Page 20: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

False DichotomyExplanation: The arguer suggests there are only two

alternatives, love America or leave it. By “love America” I take this to mean “do not criticize her.” But it is possible to “love America” and to criticize her in a constructive manner.

If you don’t love America then just get the hell out.

Page 21: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Fallacies of Sense

where the meaning either of premises or conclusions remains dubious thus clouding the overall argument structure. – Equivocation – Amphiboly

Page 22: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Equivocation

where a conclusion depends on a word or set of words whose meaning is not the same as that used in the premises.– æquus "equal" + vocare "to call“

words or phrases used as if they have the same meaning in two different contexts where they do not

Page 23: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Equivocation

Some have argued that it’s inappropriate for the press to investigate the private lives of public officials, movie stars, members of royal families, and other celebrities. However, the public has a right to know what is in the public interest, such as in cases of the government’s raising taxes, its military expenditures, etc. The private lives of celebrities are also in the public interest, and since it’s appropriate to make known what is in the public interest, it really is appropriate for the press to investigate the private lives of celebrities.

Page 24: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

Some have argued that it’s inappropriate for the press to investigate the private lives of public officials, movie stars, members of royal families, and other celebrities. However, the public has a right to know what is in the (1) public interest, such as in cases of the government’s raising taxes, its military expenditures, etc. The private lives of celebrities are also in the (2) public interest, and since it’s appropriate to make known what is in the public interest, it really is appropriate for the press to investigate the private lives of celebrities.

Page 25: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

Equivocation

Definition: where a conclusion depends on a word or set of words whose meaning is not the same as that used in the premises.

Explanation: The phrase “public interest” is used in two distinct senses. First, “public interest” means the goods and expenditures common to society collectively, e.g., taxes, military expenditures, etc. Second, it means the interest of private individuals about popular subjects, e.g., the interest by many in the lives of celebrities. The argument treats these two as equivalent expressions.

Page 26: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Amphiboly

where a syntactically ambiguous premise (e.g., a mistake of grammar or punctuation) leads to a false conclusion.

For Example:

A reckless motorist injured a student in his pickup truck Thursday who was jogging through campus. So kids, don’t jog in pickup trucks. It’s very unsafe.

Page 27: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

Amphiboly

Definition: where a syntactically ambiguous premise (e.g., a mistake of grammar or punctuation) leads to a false conclusion.

Explanation: The phrase “who was jogging through campus” refers to the injured student. The conclusion erroneously takes it to refer to the reckless motorist.

Page 28: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Whole Part Fallacies

where transfer of an attribute is illegitimate from whole to part or vice versa.– Composition: where an attribute of (all) the parts

is erroneously asserted of the whole (i.e., a genus or a class as a whole).

– Division: where an attribute of the whole is erroneously asserted of the part(s)

Page 29: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

Composition or Division?

Salt is a nonpoisonous compound. Therefore, sodium and chlorine are nonpoisonous.

Division

Page 30: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

Division

Definition: where an attribute of the whole is erroneously asserted of the part(s) .

Explanation: The attribute of the whole compound, i.e., that it is “non-poisonous,” is inferred to each element of the compound. (Each element is poisonous when isolated.)

Salt is a nonpoisonous compound. Therefore, sodium and chlorine are nonpoisonous.

Page 31: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

The CCU football team should be good next year. After all, everyone on the team is a good athlete, so the team as a whole should be good.

CompositionDefinition: where an attribute of (all) the parts is erroneously

asserted of the whole (i.e., a genus or a class as a whole).

Explanation: ???

Page 32: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluation & Critique

The CCU football team should be good next year. After all, everyone on the team is a good athlete, so the team as a whole should be good.

CompositionDefinition: where an attribute of (all) the parts is erroneously

asserted of the whole (i.e., a genus or a class as a whole).

Explanation: The attribute of each member of the team, i.e., that each is good, is inferred to apply to the whole team. (It may be the team lacks cohesiveness, so the team may not be good as a team.)

Page 33: Informal Fallacies  “A Short Catalog of Informal Fallacies”

Evaluate & Critique

If Fallacious

Identify Fallacy Concrete Explanation