| Logic sytem conforming with the principle of bivalence.
In this system possibilities are given a variable, or atomic formula. A well formed
formula is defined thus:
wff ::= wff connective wff
| not(wff)
| wff
| atomic formula
connective ::= and | or | implies | two-way implication
Implies is often written →
two-way implication is often written ↔
And is written ^
Or is written as an upside-down ^.
For example, the statement "If I am in a house, I am inside and off the streets" could be
expressed as a well formed formula of propositional logic thusly:
H -> (I ^ O)
| 
