Logic 2303 Exam 1

Need to know

Argument

A set of statements where some of the statments, called the premises, are intended to support a conclusion or belief. An argument typically seeks to demonstrate that the conclusion is true based on the premises provided.

Argument form

A structured representation of an argument that outlines the premises and conclusion, often used in logical analysis.

Logic

the study of methods for evaluating whether the premises of an argument adequately support its conclusion

Statement

a sentence that is either true or false

Deductive argument

Is one in which the premises are intended to guarantee the conclusion

Inductive argument

One in which the premises are intended to make the conclusion probable, without guaranteeing it

Valid argument

One in which it is necessary that, if the premises are true, then the conclusion is true.

Invalid argument

one in which it is not necessary that, if the premises are true, then the conclusion is true

Sound argument

a valid argument with true premises

Unsound argument

one that either is invalid or has at least one false premise

Deductive logic

the study of methods for determining whether or not an argument is valid

Argument form

a pattern of reasoning

Substitution instance

of an argument form is an argument that results from uniformly replacing the variables in that form with statements (or terms)

Valid argument form

one in which every substitution instance is a valid argument

Negation

A statement is its denial

conditional statement

an if-then statement, often simply called a "conditional"

The if-clause of a conditional is its

antecedent

The then-clause of a conditional

Consequent

disjunction

Is an either-or statement

Disjuncts

statements comprising a disjunction

Modus Ponens

If A, then B. A. So, B.

Modus Tollens

If A then B. Not B. Therefore, not A.

Hypothetical Syllogism

If A, then B. If B, then C. So, if A, then C.

Disjunctive Syllogism

Either A or B. Not A. So, B.

Constructive dilemma

Either A or B. If A, then C. If B, then D. So, either C or D.

Fallacy of Denying the Antecedent

an invalid argument form: If A, then B; not A; so, not B.

invalid argument form

is one that has some invalid substitution instances

Counterexample

to an argument form is a substitution instance in which the premises are true and the conclusion is false

good counterexample

to an argument form is a substitution instance in which the premises are well-known truths and the conclusion is a well-known falsehood.

Fallacy of Affirming the Consequent

An invalid argument form: If A, then B; B; so, A.

Categorical Statement

is a statment that relates two classes or categories, where a class is a set or collection of things.

strong argument

is one in which it is probable (but not necessary) that if the premises are true, then the conclusion is true

weak argument

is one in which it is not probable that, if the premises are true, then the conclusion is true

cogent argument

A strong inductive argument with all true premises.

uncogent argument

one that is either weak or strong with at least one false premise

Deductive Logic

is the part of logic that is concerned with the study of methods of evaluating arguments for validity and invalidity.

Inductive Logic

is the part of logic that is concerned with the study of methods of evaluating arguments for strength and weakness

Report

a set of statements intended to provide information about a situation, topic, or event

Illustration

This is a statement together with explanatory or clarifying example. Usually includes the words because, so, this, therefore, since.

Explanatory Statement

provides a reason for the occurrence of some phenomenon

Conditional statement

is an if-then statement

standard form

If A, then B. This is for a conditional statement

excess verbiage

a word or statement that adds nothing to the argument

discount

Is an acknowledgment of a fact or possibility that might be thought to render the argument invalid, weak, unsound, or uncogent.

rhetorical elements

elements in an argument that increase its psychological persuasiveness without affecting its validity, strength, soundness, or cogency

Repitition

A restatement of a premise or conclusion, perhaps with slightly altered wording

Assurance

a statement, word, or phrase that indicates that the author is confident of a premise or inference

Hedge

a statement, word, or phrase that indicates that the arguer is tentative about a premise or inference

Enthymeme

an argument with an implicit premise or conclusion

Argument Diagram

Visual representation of an argument's structure.

Diagramming Arguments

First, place brackets around each statement in the argument. Then draw an arrow from the premise to the conclusion.

Formal fallacy

an error in reasoning that involves the explicit use of an invalid form

informal fallacy

an error in reasoning that does not involve the explicit use of an invalid form

argument against the person (ad hominem)

Involves attacking the person who advances an argument (or asserts a statement) as opposed to providing a rational critique of the argument (or statement) itself.

Abusive Ad Hominem

involves an attempt to discredit an argument or view by launching a direct personal attack

Circumstantial Ad Hominem

involves an attempt to discredit an argument or view by calling attention to the circumstances or situation of those who advance it

Tu Quoque Fallacy

involves an attempt to discredit an argument or view by suggesting the arguer is hypocritical

straw man fallacy

occurs when the arguer attacks a misrepresentation of the opponent's view

appeal to force (ad baculum)

occurs when a conclusion is defended by a threat to the well-being of those who do not accept it

Appeal to the People (Ad Populum)

an attempt to persuade a person or group by appealing to the desire to be accepted or valued by others

Appeal to Pity (Ad Misericordiam)

the attempt to support a conclusion merely by evoking pity in one's audience

Appeal to Ignorance

Involves one of the following: either (a) the claim that a statement is true (or may be reasonably believed true) simply because it hasn't been proven false or (b) the claim that a statement is false (or may be reasonably believed false) simply because it hasn't been proven true

red herring fallacy (ignoratio elenchi)

occurs whenever the premises of an argument are logically unrelated to the conclusion

Fallacy of Equivocation

occurs when multiple meanings of a word (or phrase) are used in a context where validity requires a single meaning of that word (or phrase)

Fallacy of Amphiboly

occurs when multiple meanings of a sentence are used in a context where (a) validity requires a single meaning and (b) the multiple meanings are due to sentence structure

Fallacy of composition

involves either (a) an invalid inference from the nature of the parts to the nature of the whole or (b) an invalid inference from attributes of members of a group to attributes of the group itself

Fallacy of Division

involves either (a) an invalid inference from the nature of the whole to the nature of the parts or (b) an invalid inference from the nature of a group to the nature of its members

begging the question (Petition principii fallacy)

Occurs when an argument assumes the point to be proved.

False Dilemma

occurs when one uses a premise that unjustifiably reduces the number of alternatives to be considered

appeal to unreliable authority (ad verecundiam fallacy)

is an appeal to an authority when the reliability of the authority may be reasonably doubted

false cause fallacy (post hoc, ergo propter hoc)

occurs when one possible cause of a phenomenon is assumed to be a (or the) cause although reasons are lacking for excluding other possible causes

Complex Question Fallacy

involves asking a question that illegitimately presupposes some conclusion alluded to in the question

slippery slope fallacy

occurs when we assume one action will initiate a chain of events that culminate in an undesirable event

Intentional Fallacy

the fallacy of basing an assessment of a work on the author's intention rather than on one's response to the actual work

Is-Ought Fallacy

Is an argument that proceeds from non-moral premises to moral conclusions

Premises

are statements offered in support

Conclusion

The claim that needs support