Logic and Critical Thinking Unit Seven: Argument in Logic (II)

These flashcards cover the definitions and categories of deductive and inductive arguments, specific argumentative forms, and the criteria for evaluating arguments including validity, soundness, strength, and cogency.

Conclusion

A claim—some statement of fact or opinion—that represents the point an argument is trying to make.

Premises

Supporting lines of reasoning that provide evidence or reasons related to a claim.

Deductive Argument

An argument whose conclusion is claimed to follow from its premises with absolute necessity or conclusive grounds.

Inductive Argument

An argument that claims its premises provide some degree of probability, but not certainty, to its conclusion.

Deductive Indicator Words

Words that suggest a deductive argument, such as "certainly," "necessarily," "absolutely," and "definitely."

Inductive Indicator Words

Words that suggest an inductive argument, such as "probable," "improbable," "plausible," "implausible," "likely," "unlikely," and "reasonable to conclude."

Argument based on Mathematics

A deductive argument in which the conclusion depends on some purely arithmetic or geometric computation or measurement.

Argument based on Definition

A deductive argument where the conclusion is claimed to depend merely on the definition of some word or phrase used in the premise or conclusion.

Syllogism

A deductive argument consisting of exactly two premises and one conclusion.

Modus Ponens

A deductive form also known as affirming the antecedent: $If\ A\ then\ B$; $A$; Therefore, $B$.

Modus Tollens

A deductive form also known as denying the consequent: $If\ A\ then\ B$; $Not\ B$; Therefore, $not\ A$.

Hypothetical Syllogism

A syllogism having a conditional statement for one or both of its premises, following the form: $If\ A\ then\ B$; $If\ B\ then\ C$; Therefore, $if\ A\ then\ C$.

Disjunctive Syllogism

A syllogism containing a disjunctive statement (an "either… or" statement).

Prediction

An inductive argument that proceeds from knowledge of the past to a claim about the future.

Argument from Analogy

An inductive argument that depends on the existence of a similarity between two things or states of affairs to conclude that a condition affecting one also affects the other.

Inductive Generalization

An argument that proceeds from the knowledge of a selected sample to some claim about the whole group.

Argument from Authority

An inductive argument in which the conclusion rests upon a statement made by some presumed authority or witness.

Argument based on Signs

An inductive argument that proceeds from the knowledge of a certain sign to the knowledge of the thing or situation that the sign symbolizes.

Causal Inference

An inductive argument that proceeds from the knowledge of a cause to an effect, or conversely, from an effect to a cause.

Valid Deductive Argument

An argument in which it is necessary that, if the premises are true, then the conclusion must be true.

Invalid Deductive Argument

An argument where, even if the premises are assumed true, it is possible for the conclusion to be false.

Sound Argument

A deductive argument that is both valid and has all true premises ($Sound\ Argument = A\ valid\ argument + All\ true\ premises$).

Unsound Argument

A deductive argument that is either invalid, or valid with one or more false premises.

Strong Inductive Argument

An inductive argument where the premises provide significant support, making it probable that the conclusion is true.

Weak Inductive Argument

An inductive argument where the premises do not provide enough support to make the conclusion probable.

Cogent Argument

An inductive argument that is strong and has all true premises ($Cogent\ Argument = A\ strong\ argument + All\ true\ premises$).

Uncogent Argument

An inductive argument that is either weak, or strong with one or more false premises.