- |

Biconditional
Any two propositions P if and only if Q
P if and only if Q is true if and only if both P
and Q are true, or if both P and Q are false.
It is false only when one of them is true and the other false.
The truth table for Not PQ is
as follows:
If you have Java, try it out for yourself:
Set the truth values for the propositions
**P if and only if Q**is the same as:**( If P then Q ) and ( P only if Q )**. This is like saying:**( If P then Q ) and ( If Q then P )**.
if and only if operator plays a special role in
definitions. When we say
P if and only if q, we are saying that P says the same
thing as Q.
For Educators Stephen Downes Guide to the Logical Fallacies Copyright © Stephen Downes, 1995-2001 stephen.downes@ualberta.ca |