1. In this way the propositional calculus can be discarded entirely. 2. The underlying logic is classical propositional calculus and classical predicate calculus with equality. 3. This is expressed in a propositional calculus as logical equivalence of certain compound statements. 4. Our propositional calculus has ten inference rules. 5. Modal logic also offers a variety of inferences that cannot be captured in propositional calculus . 6. It is not that these rules are contentious, when applied in conventional propositional calculus . 7. In fact the sign comes into the propositional calculus when a formula is to be evaluated. 8. RHS ( in propositional calculus ), then LHS = RHS ( in Boolean algebra ). 9. Classical propositional calculus as described above is equivalent to intuitionistic propositional calculus is equivalent to Heyting algebra. 10. Classical propositional calculus as described above is equivalent to intuitionistic propositional calculus is equivalent to Heyting algebra.
