Introduction to Propositional Logic

Study Notes

Introduction to Propositional Logic

A statement is a declarative sentence that can be classified as true (1) or false (0).
True and false correspond to 1 and 0 in Boolean logic, which is commonly used in philosophy.
Examples of statements include:
- "Milk is white" (generally true, but not for chocolate milk).
- "The cardinality of the empty set is equal to zero" (true).
- "Humans are just fish with legs" (false).

Non-Statements

Questions cannot be classified as true or false, e.g., "Will you go to the store for me?"
Imperatives (commands) also do not have truth values, e.g., "Kick me."

Propositions vs. Statements

Statements are specific, while propositions capture the general idea.
Propositions are typically denoted with capital letters (e.g., P, Q, R) for specific meanings.
Lowercase letters (e.g., p, q, r) represent general propositions without specific context.

Well-Formed Formulas (WFF)

A statement or proposition can be a well-formed formula (WFF) within propositional logic.
"Not P" is a WFF representing negation.
The logical conjunction "P and Q" connects two WFFs, represented as P ∧ Q.
The logical disjunction "P or Q" is represented as P ∨ Q.
Conditional statements "if P then Q" are denoted as P → Q.

Translating Well-Formed Formulas into English

Translating logical expressions into plain English involves understanding the logical connectives.
Example translation:
- Given R (I write an exam), P (I cheat), Q (I will get caught), S (I will fail):
- The formula "R and P → Q and S" translates to:
  - "If I write an exam and I cheat, then I will get caught and I will fail."

Key Connectives in Propositional Logic

Negation: ¬P (not P)
Conjunction: P ∧ Q (P and Q)
Disjunction: P ∨ Q (P or Q)
Conditional: P → Q (if P then Q)

Summary

Understanding propositions, well-formed formulas, and connectives is fundamental to mastering propositional logic.
Translating logical expressions properly helps clarify their meanings in natural language.

Description

This quiz focuses on the basics of propositional logic and the translation of English sentences into logical statements. You will learn about the nature of statements, their truth values, and how they relate to boolean logic. Get ready to explore the foundational concepts that underpin logical reasoning.