Tautologies, contradictions and contingencies
- A compound proposition that is always true (no matter what
the truth values of the propositions that occur in it), is called a
- A proposition that is always false is called a contradiction.
The truth table for a tautology has “T” in every row.
The truth table for a contradiction has “F” in every row.
- A proposition that is neither a tautology nor a contradiction is
Contingencies have both “T”s and “F”s in their truth tables.