ABSTRACT
In Truth-Functional Logic, each rule could be applied to either statements or statement forms; for example the rule of simplification could be applied directly either to a statement, e.g. Dogs bark.lions roar, or to a statement form, e.g.p.q. The rules which have just been listed on the other hand are to be applied directly only to statements. A broad characteristic of deductive systems in general is illustrated here: shorter deductions require more numerous or more complex rules. An actual deduction is of course correctly constructed if each step is taken in accordance with one of the listed rules. A deduction schema on the other hand may be regarded as correctly constructed if every actual deduction which exemplified the schema would be correctly constructed.
