PHIL 105 — Propositional Logic Lecture Notes

A collection of flashcards on key concepts from propositional logic, including definitions and logical structures.

¬p

Not (negation of proposition p)

p • q

And (conjunction of propositions p and q)

p ∨ q

Or (disjunction of propositions p and q)

p → q

If p then q (conditional statement)

p ↔ q

Equivalent (biconditional statement between p and q)

Tautology

A statement that is always true.

Contradiction

A statement that is always false.

Validity (Arguments)

An argument is valid if there is no case where premises are true and conclusion is false.

Obversion

A valid operation that changes the quality and negates the predicate.

Conversion

A valid operation for E and I forms, limited for A form.

Contraposition

Valid operation for A and O forms.

Major term

The predicate of the conclusion in a syllogism.

Minor term

The subject of the conclusion in a syllogism.

Middle term

The term that appears in both premises.

Square of Opposition

A diagram representing the relations between the four types of categorical propositions.

Validity check with Venn diagrams

A method to visually determine the validity of syllogistic arguments.

Translation trap: 'p only if q'

Translates to p → q.

Translation trap: 'p if q'

Translates to q → p.

Translation trap: 'p unless q'

Translates to ¬q → p.

Translation trap: 'either p or q'

Translates to p ∨ q.