Logic and Ethics Flashcards

In a valid deductive argument, if the premises are true, the conclusion must be:

Answer: Necessarily true

Validity means the truth of the premises guarantees the truth of the conclusion—the conclusion cannot be false if the premises are true.

Which logical form represents a valid modus ponens argument?

Answer: If P then Q; P; therefore Q

Modus ponens ('affirming the antecedent') infers Q from the conditional 'If P then Q' together with P.

The logical form 'If P then Q; not Q; therefore not P' is known as:

Answer: Modus tollens

Modus tollens ('denying the consequent') is a valid inference that negates the antecedent when the consequent is denied.

A proposition that is true under every possible interpretation is called:

Answer: A tautology

A tautology is necessarily true by virtue of its logical form alone, regardless of the truth values of its components.

In categorical logic, the statement 'No S is P' is classified as:

Answer: A universal negative (E proposition)

The E proposition universally denies the predicate of the entire subject class.

Which of the following best illustrates inductive reasoning?

Answer: Every swan observed so far has been white; therefore all swans are white

Inductive reasoning moves from observed instances to a general conclusion that goes beyond the evidence and remains uncertain.

Two propositions are logically equivalent when:

Answer: They have the same truth value in every possible situation

Logical equivalence means the two propositions agree in truth value under all possible assignments of truth values to their components.