Show that the following statement pattern is contingency.
(p → q) ↔ (~ p ∨ q)
SOLUTION
| p | q | ~p | p→q | ~p∨q | (p→q)↔(~p∨q) |
| T | T | F | T | T | T |
| T | F | F | F | F | T |
| F | T | T | T | T | T |
| F | F | T | T | T | T |
All the truth values in the last column are T. Hence, it is a tautology. Not contingency.
