Symbolic logic Logic is formalization of thought. Persons gain new knowledge from some knowledges by thinking. The simplest formula is usually represented by an alphabet and denotes simple phenomena. These simple formulas are called atomic formulas. Some formulas are connected and made into a new formula.
Logical operators connect formulas.
The knowledge consist of many knowledges. Thus we consider some sets of formulas. A set of formulas is denoted by a capitalized Greek letter. Sequent is used to represent knowledge. A sequent represents that if all elements of one set of formulas is correct, some elements of another set of formulas is correct.