Symbolic Logic

Symbolic Logic explores the principles of formal reasoning and the use of symbols to represent logical expressions.

Basic Concepts

Truth Tables and Logical Equivalence

What Is a Truth Table?

A truth table lists every possible combination of truth values for the given propositions. It helps us understand how logical connectives work together.

Logical Equivalence

Two statements are logically equivalent if they always have the same truth value, no matter what. We use this to check if two arguments are really saying the same thing.

Building Truth Tables

  1. List all possible truth values for the basic propositions.
  2. Combine them using connectives.
  3. Compare the final columns to check for equivalence.

Example: Double Negation

The statement \( \lnot(\lnot p) \) is always equivalent to \( p \), which we can see using a truth table.

\( p \)\( \lnot p \)\( \lnot(\lnot p) \)
TFT
FTF

Examples

  • Checking if \( p \rightarrow q \) and \( \lnot p \lor q \) are logically equivalent using a truth table.

  • Proving that \( p \lor \lnot p \) is always true—this is called a tautology.

In a Nutshell

Truth tables help us compare logical statements and see if they are really the same.