Abstract

It is sometimes objected that Tichý’s logic is not a logic because it underestimates deduction, providing only logical analyses of expressions. I argue that this opinion is wrong. First of all, to detect valid arguments, which are formulated in a language, there needs to be logical analysis to ascertain which semantical entities are involved. Entailment is defined as an extralinguistic affair relating those constructions. The validity of an argument, composed of propositional constructions, stems from the properties of the constructions. Such properties are displayed by the derivation rules of Tichý’s system of deduction