The rule makes it possible to eliminate a disjunction from a logical proof.

During this stage the adolescent is able to understand such things as love, "shades of gray", logical proofs and values.

The rule allows one to introduce or eliminate a negation from a logical proof.

The rule makes it possible to introduce a conjunction into a logical proof.

Perhaps it has no philosophical verity, but the things men live by are rarely subject to logical proof.

And the spirit gives him logical proof in an unexpected burst of enthusiasm for man.

He did not use reason, logical proof, myth, or allegory.

Along the way, he advances another logical proof of God's existence.

A logical proof is a list of statements.

The rule makes it possible to introduce disjunctions to logical proofs.