A
B
~A
~B
(
~
A
⊃
~
B)
(
~B
⊃
~A
)
(~A
⊃
~B)
≡
(~B
⊃
~A)
T
T
F
F
T
T
T
T
F
F
T
T
F
F
F
T
T
F
F
T
F
F
F
T
T
T
T
T
Logical Status:
contingency