Formal Notation
The disjunction introduction rule may be written in sequent notation:
where is a metalogical symbol meaning that is a syntactic consequence of in some logical system;
and expressed as a truth-functional tautology or theorem of propositional logic:
where and are propositions expressed in some formal system.
Read more about this topic: Disjunction Introduction
Famous quotes containing the word formal:
“That anger can be expressed through words and non-destructive activities; that promises are intended to be kept; that cleanliness and good eating habits are aspects of self-esteem; that compassion is an attribute to be prized—all these lessons are ones children can learn far more readily through the living example of their parents than they ever can through formal instruction.”
—Fred Rogers (20th century)